AMERICAN HANDBOOK OF THE DAGUERREOTYPE
Project Gutenberg Etext #167: September, 1994
Giving The Most Approved And Convenient Methods For
Preparing The Chemicals, And The Combinations Used In The
Art. Containing The Daguerreotype, Electrotype, And Various
Other Processes Employed In Taking Heliographic
Impressions.
By S. D. HUMPHREY
Fifth Edition, 1858
New York: Published By S. D. Humphrey
37 Lispenard Street
Entered, according to Act of Congress, in the year 1858, by S. D. HUMPHREY, In
the Clerk's Office of the District Court of the Southern District of New York.

To J. Gurney, whose professional skill, scientificaccuracy, and energetic perseverance, have won for him
universal esteem, this work is most respectfully inscribed.

Preface
There is not an Amateur or practical Daguerreotypist, who has not felt the wantof a manual--Hand Book, giving concise and reliable information for theprocesses, and preparations of the Agents employed in his practice.
Since portraits by the Daguerreotype are at this time believed to be more
durable than any other style of "Sun-drawing," the author has hit upon thepresent as being an appropriate time for the introduction of the Fifth Editionof this work. The earlier edition having a long since been wholly; exhausted,
the one now before you is presented.
The endeavor has been to point out the readiest and most approved Methods ofOperation, and condense in its pages; as much practical information as its
limits will admit. An extended Preface is unnecessary, since the aim and scopeof this work are sufficiently indicated by the title.
S. D. HUMPHREY NEW YORK, 1858.

CONTENTS
CHAPTER I
Polishing the Daguerreotype Plate--Buffing the Plate--Coating the Plate-Exposure of the Plate in the Camera--Position Developing the Daguerreotype-Exposure to Mercury--Removing the Coating--Gilding or fixing the Image--Coloring
Daguerreotype.
CHAPTER II
Coloring Back Grounds--Transparent ditto--Gilding Dissolvent--Solution forremoving Specks--Solarized Impression--To Purify Water--Cleaning Mercury-Adhesive Paper--Black Stain for Apparatus--Sealing Wax for Bottles--Rouge-Rotten Stone--Potassa Solution--Hyposulphite Solution--Substitute for do.-Gilding Solution--Solution for increasing the Brilliancy of the Daguerreotype-Bleaching Solution;--Cold Gilding--Neutralizing Agents--Buff Dryer--Keeping
Buffs in order--Cleaning Buckskins--Reflector for taking Views.
CHAPTER III
Bromine and its Compounds--Iodine and its Compounds--Chlorine and its Compounds-Cyanide of Potassium--Hyposulphite of Soda--Hyphosulphite of Gold--Nitric Acid-Nitro-Muriatic Acid--Hydrochloric Acid--Hydrofluoric Acid--Sulphuric Acid-Accelerating Substances--Liquid Sensitives--Dry Sensitives, etc.
CHAPTER IV
Light--Optics--Solar Spectrum--Decomposition of Light--Light, Heat, andActinism--Blue Paper and Color for the Walls of the Operating Room--Proportionsof Light, Heat and Actinism composing a Sunbeam--Refraction--Reflection--Lenses-Copying Spherical Aberration--Chromatic Aberration.
CHAPTER V
To make Plates for the Daguerreotype--Determining the Time of Exposure in the
Camera--Instantaneous Process for Producing Daguerreotype--Galvanizing theDaguerreotype Plate--Silvering Solution--Daguerreotype without Mercury-Management of Chemicals--Hints and Cautions--Electrotyping--Crayon
Daguerreotypes--Illuminated Daguerreotypes--Natural Colors in Heliography-Multiplying Daguerreotypes on one Plate--Deposit in Gilding--Practical Hints on
the Daguerreotype.
CHAPTER VI
An Account of Wolcott and Johnson's Early experiments in the Daguerreotype.

CHAPTER I
Polishing the Daguerreotype Plate--Buffing the Plate--Coating the
Plate--Exposure of the Plate in the Camera--Position--Developing theDaguerreotype--Exposure to Mercury--Removing the Coating--Gilding or
fixing the Image--Coloring Daguerreotype.
Polishing the Daguerreotype Plate.
I shall endeavor to present to the reader the process I have found productive ofgood and satisfactory results, presenting the same in a clear and concise
manner, so that any one, by following the various manipulations given, will beenabled to succeed. If there is any one part of the process in Daguerreotype inwhich operators fail more than all others, it is in not properly preparing theplate. It has truly been said that it would take a volume to describe all themethods that have been suggested for polishing the plate.
I shall confine myself to the following description, which has been successfully
practised, also most generally adopted by our operators, and I believe equal, if
not superior to any other method, yet at the same time it is not of so much
importance what particular method is employed, so that it be thoroughly andskillfully carried out.
There is a general tendency with beginners to slight this operation; hence thenecessity of adopting a system which precludes the possibility of doing so.
During many years' study and practice in the art, I have tried numerous methods
and substances for the better accomplishment of the end in view, and havefinally settled upon the following, as being (so far as experience allows me toJudge) the modus operandi, best suited to all circumstances; under no condition
would I approve of a method less rigorous or precise.
The operator being provided with a bottle of finely prepared rotten stone, cover
the mouth of the bottle with a piece of thick paper, this perforated with a pin
so that the rotten stone can be dusted on the plate. Fasten the plate on theholder, take the rotten stone (Becker's can always be depended upon), and duston lightly until the surface is freely covered; now drop on the plate's surface
a few drops of an alcoholic solution.*
Take a patch of Canton flannel; in order to prevent the moisture from the hand
it should have a thick, firm texture: with this rub the plate in circles across,then back covering one half of the former row of circles in each crossing until
you have gone over the plate and back to the point of beginning, occupying at* This solution is composed of equal parts of alcohol and water, for the summer,
and in winter three parts alcohol to one of water; a few drops of potassa
solution may be added, and is known to have a decided effect upon the plate.

least half a minute in the operation, for a small plate, and so in proportion
for the other sizes.
Care should be observed to keep the patch wet with the alcoholic solution
forming a paste on the surface of the plate; the motion of the hand should be
brisk and free, not hurried, and the pressure about equal to that of a pound
weight. When the cotton is disposed to adhere to the plate, and slip from under
the finger, spread the fore and middle fingers a little apart, then pressing
down, bring them together in such a manner as to form a fold in the cloth
between them, by which means you will hold it perfectly secure.
Avoid wetting the fingers, and should they perspire, wipe them often, as the
moisture penetrating the cotton and coming in contact with the plate, would
cause streaks it would be difficult to remove. I will here remark that many
operators use much more cotton flannel than there is need of. I have found in myexperience that a single patch, about one and half inch square, will be betterfor cleaning a number of plates than a new piece for every plate. This is thecase for the wet, and for the dryrubbing two or three pieces will be found toanswer. Thus with four or five cloths a dozen plates may be prepared.
Some operators use prepared cotton, and think it more convenient than theflannel. This may be had prepared free from seeds and in a very perfect state,
if wished.
In going over the plate, great care should be observed, in touching its surface
as equally as possible. The greatest care should be taken neither to touch theplate with the fingers, nor that part of the cotton flannel which is to come incontact with its surface; take a clean piece of flannel by one corner, snap it
smartly to free it from dust and loose fibres, lay it face-side upward, dust on
a little fine rotten stone; with this, polish around, or across, or in circles,
lightly and briskly, passing gradually over the whole surface of the plate, as
was done before with the wet. The plate should now exhibit a bright, clear,
uniform surface, with a strong metallic lustre, perfectly free from any
appearance of film; if not, the last polished should be continued until theeffect is obtained, and when once obtained, the plate is ready for buffing.
Buffing the Plate.
There are a variety of ways and means employed in this part of the operation.
Some choose wheels, and others prefer the ordinary hand-buff. I have been unable
to detect any peculiar advantage in the use of the wheel except in the facilityof the operation; no doubt, however, but there is a saving of time, particularlyin the preparation of the larger plates. For general use, we have not seen awheel better adapted for this purpose than the one patented by Messrs. Lewis.
It is generally well to use a hand-buff before placing the plate on the wheel;
this is in order to prevent, as far as possible, the dust or other substancethat may be on the surface of the plate from coming in contact with the cover ofthe wheel. I will here follow out the use of the hand-buffs (two are necessary)as they are mostly used.
In the morning, before using the buffs, brush both as clean as possible, inorder to free them from dust; then with the blade of a pair of shears, held
perpendicular, rub the buffs from end to end; then knock them both together inorder to free them from all dust or other substances, occasionally exposing themto the sun or to the fire.
With one of the buffs (reserving the finest and softest for the last operation),
powder its face with fine rouge and brush off slightly, leaving only the finest
particles in it. Every operator should have two plate-holders; one for cleaningand one for buffing the plate; for when using only one, the rotten stone isliable to get on the buff and scratch the plate.
Rest the fingers of the left hand on the back of the buff, near the farther end,
with about the same pressure as in cleaning, while with the right you bear on
the handle to correspond, and give the buff a free, easy, horizontal motion,
passing it very nearly the whole length over the plate each time. Continue thisoperation in such a manner that the plate will on all parts of its surface havereceived an equal amount of polish. This buff once well filled with polish, add
but little after, say a small quantity once in two or three plates. The polishas well as the buffs must be kept perfectly dry.
The second buff should always be in the best order, and if this is the case, butlittle polish after the first need be used. Much depends upon the last finish of
the surface of the plate, and as a fine impression is desired in the same ratio,
the operator must exercise care and skill in this operation. Some buff thesmaller plates on the hands, by resting them on the fingers in such a mannerthat the buff cannot touch them; some by holding the edges with thumb and little
finger, with the remaining fingers under, or on the back; and others buff on theholder. When this last method is adopted, it requires the greatest caution toprevent the dust from getting on the buff. The holder should be wiped clean.
The plate frequently slips off or around, and the buff comes in contact with the
bed of the holder. When, however, the operator is so unfortunate as to meet withthis mishap, the utmost care must be observed in thoroughly cleaning the buff
cover before further buffing. In this last buffing it may be continued as
before, except without the application of polish powder to the last buff.
Examine the surface occasionally, and buff more lightly towards the close of theoperation, using at last the mere weight of the buff. This last buffing should
occupy as long a time as the first.
The point to be aimed at is, the production of a surface of such exquisite
polish as to be itself invisible, like the surface of a mirror. The secret of
producing pictures discernible in any light, lies in this: the more dark, deep
and mirror-like the surface of the plate, the more nearly do we approach toperfection.

In all cases, very light and long continued buffing is productive of the greater
success, since by that means a more perfect polish can be obtained.
The question is often asked, why is it that the plates receive the coating so
unevenly? I will answer by saying that it may arise from two causes: the firstand most general cause is that those parts of the plate's surface which will
receive the heaviest coating have been more thoroughly polished, and theconsequence is that it is more sensitive to the chemical operation. second. andmight perhaps be considered a part of the first, the heat of the plate may not
be equal in all its parts; this may arise from the heat caused by the friction
in buffing. It is a well known fact, with which every observing practitioner isfamiliar, that a silver plate at a temperature of 45 deg. or less, exposed to
the vapors of iodine, is less sensitive and takes a longer time to coat, thanwhen it is at a temperature of 60 deg. or more.
Whenever a view is to be taken, or any impression which requires the plate to beturned on the side, it should be buffed in the other direction, so that themarks will always be horizontal, when the picture is in position. With thefinest possible polish, the plate is ready for the coating box.
The question is often asked by operators, what is the state of the plate when
polished and allowed to stand for a time before using? To meet this point wehare only to consider the silver and the power acting upon it. Pure atmospheredoes not act upon silver; but we do not have this about in our operating rooms,
as it is more or less charged with sulphurated hydrogen, which soon tarnishes
the surface of the plate with a film of brown sulphurate. It is this thatsometimes causes the specks which appear on finishing the impression, and are agreat annoyance. Hence we see that the plate should be buffed just before
receiving the vapor of iodine. Mr. Hunt gives his opinion of the use of diluted
nitric acid as the best solution for freeing, the surface of the plate; he says:
Numerous experiments on plated copper, pure silver plates, and on silvered
glass and paper, have convinced me that the first operation of polishingwith nitric acid, etc., is essential to the production of the most sensitive
surface. All who will take the trouble to examine the subject, will soon beconvinced that the acid softens the silver, bringing it to a state in which
it is extremely susceptible of being either oxydized or iodized, according
as the circumstances may occur of its exposure to the atmosphere or theiodine.

I cannot see the objection to this solution; not, however, in general use. Ouroperators do not find it of sufficient importance to the success of their
pictures to accept it, the alcoholic solution being in its nature lessobjectionable.
I will say here, that a plate submitted to only an ordinary polish is found tocontain numberless minute particles of the powder made use of. Should the sameplate be buffed for a long time, the polish will nearly all disappear, leaving

the cavities in the surface free for the action of agents employed in subsequent
operation. For this reason, I find that great amount of polishing powder should
not be applied to the last buff, and it is obvious that three buffs can be
employed to adventure; the two last should not receive any polishing materials.
I have examined a plate that was considered to possess a fine finish, andsimilar had produced good impressions; these same plates, when subjected to along and light buffing, would present a surface no finer in appearance to thenaked eye; but upon exposure to the solar radiation, would produce a welldefined image in one fourth less time than the plate without the extra buffing.
Coating the Plate.
For this purpose our mechanics and artists have provided a simple apparatus
called a coating-box, which is so arranged as to be perfectly tight, retaining
the vapor of the iodine or accelerators, and at the same time allowing, by meansof a slide, the exposure of the plate to these vapors. They can readily beobtained by application to any dealer, all of whom can furnish them.
The principal difficulty in coating the plate, is that of preserving the exact
proportion between the quantity of iodine and bromine, or quick. It is here
necessary to say, that hardly any two persons see alike the same degree ofcolor, so as to be enabled to judge correctly the exact tint, i. e. what one
might describe as light rose red, might appear to another as bright or cherry
red; consequently, the only rule for the student in Daguerreotype, is to study
what appears to him to be the particular tint or shade required to aid him to
produce the desired result. Practise has proved that but a slight variation in
the chemical coating, of the Daguerreotype plate will very materially affect the
final result.
The operator will proportion the coating of iodine and bromine or accelerators
according to the strength and composition of the latter.
Experience proves that the common impressions, iodized to a rather light yellow
gold tint, and brought by the bromine to a very light, rose color, have their
whites very intense, and their deep shades very black. It is also known that if
you employ a thicker coating of iodine and apply upon it a proportionate tint ofbromine, so as to obtain a deep rose tint, delineations will be less marked, andthe image have a softer tone. This effect has been obvious to everyone who haspractised the art. Thus I may observe that the light coatings produce strong
contrast of light and shade, and that this contrast grows gradually less, untilin the very heavy coating it almost wholly disappears. From this it will readily
be perceived that the middle shades are the ones to be desired for representing
the harmonious blending of the lights and shades.
Then, if we examine, with respect to strength, or depth of tone, and sharpnessof impression, we see that the light coating, produces a very sharp but shallow
impression; while the other extreme gives a deep but very dull one. Here, then,are still better reasons for avoiding either extreme. The changes through whichthe plate passes in coating may be considered a yellow straw color or darkorange yellow, a rose color more or less dark in tint, or red violet, steel blueor indigo, and lastly green. After attaining this latter color, the plate
resumes a light yellow tint, and continues to pass successively a second time,with very few exceptions, through all the shades above mentioned.
I will here present some excellent remarks upon this subject by Mr. Finley. Thisgentleman says:
It is well known to all who have given much attention to the subject, thatan excess of iodine gives the light portions of objects with peculiar
strength and clearness, while the darker parts are retarded, as it were, andnot brought out by that length of exposure which suffices for the former.
Hence, statuary, monuments, and all objects of like character, wereremarkably well delineated by the original process of Daguerre; the plate
being coated with iodine alone. An excess of bromine, to a certain degree,
has the opposite effect; the white portions of the impression appearing of adull, leaden hue, while those which should be black, or dark, appear quite
light. This being the case, I conclude there must be a point between the two
extremes where light and dark objects will be in photogenic equilibrium. The
great object, therefore, is to maintain, as nearly as possible, a perfectbalance between the two elements entering into union to form the sensitive
coating of the plate, in order that the lights and shades be truly andfaithfully represented, and that all objects, whether light or dark, be madeto appear so far conformable to nature, as is consistent with the differencein the photogenic energy of the different colored rays of light. It is thisnicely-balanced combination which ensures, in the highest degree, a union of
the essential qualities of a fine Daguerreotype, viz., clearness andstrength, with softness and purity of tone.
So far as I know, it is the universal practice of operators to judge of the
proportion of iodine and bromine in coating the plate, by two standards ofcolor the one fixed upon for the iodine, the other for the additional
coating of bromine. Now I maintain that these alone form a very fallacious
standard. first, because the color appears to the eye either lighter or
darker, according as there is more or less light by which we inspect thecoating; and secondly, because if it occur that we are deceived in obtaining
the exact tint for the first coating, we are worse misled in obtaining thesecond, for if the iodine coating be too light, then an undue proportion ofbromine is used in order to bring it to the second standard, and vice versa.

The iodine box should be kept clean and dry. The plate immediately after thelast buffing, should be placed over the iodine, and the coating will depend upon
the character of the tone of the impression desired. Coating over dry iodine toan orange color, then over the accelerator, to a light rose, and back overiodine one sixth as long as first coating, will produce a fine, soft tone, andis the coating generally used for most accelerators. The plate iodized to a darkorange yellow, or tinged slightly with incipient rose color, coated over theaccelerator to a deep rose red, then back over iodine one-tenth as long as atfirst coating, gives a clear, strong, bold, deep impression.

I will here state a singular fact, which is not generally known to the operator.
If a plate, coated over the iodine to a rose red, and then exposed to strong dry
quick or weak bromine water, so that a change of color can be seen, thenrecoated over the iodine twice as long as at first coating, it will be found far
more sensitive when exposed to the light than when it has been recoated over theiodine one-fourth of the time of the first coating.
Probably the best accelerating combination is the American compound formerly
known as "Gurney's American compound," or some of the combinations of bromide oflime. The first is thought to possess perhaps more uniformity in its action thanany other combination I have ever used.
The plate once coated should be kept excluded from the light by means of theplate holder for the camera box.
I will notice one of the principal causes having a tendency to prevent theperfect uniformity of chemical action, between the iodine and silver; hydrogen,or the moisture in the atmosphere, makes a very perceptible barrier. Thismoisture may arise as the result of the cold, from a want of friction in thebuffing of the plate, which, coming in contact with the warmer air, as a writeron this subject says:"It is well known that as often as bodies, when cold, are exposed to a warmer
air, the humidity contained in them is condensed. It is to this effect that wemust attribute the difficulty experienced in operating in most cases." This iscorroborated by the results experienced by our operators. So it is seen that theplate should be of a temperature above that of the atmosphere. Mr. Gurney
submits his plates to a gentle heat from a spirit lamp just before exposing themto the vapor of iodine. Experience has convinced me that a plate heated to about
80 deg. before being exposed to iodine will present a far better defined image
than a plate at a temperature of 50 deg. I account for this by noticing that, at
a higher temperature, the plate throws off any larger crystals that mightotherwise be deposited, receiving only the finer, thus producing a more perfectchemical combination of iodide of silver. I would call the attention of theoperator to this point, as presenting something of interest, and which may
direct in a way of accelerating the future operations.
That the presence of a film of moisture over the plate is a preventive of
uniform chemical action, may be readily understood from the fact that iodine isalmost insoluble in water, requiring seven thousand parts of water to dissolve
one of iodine, or one grain to a gallon of water. Yet its affinities for silver
and other substances are so powerful as to prevent its existing in an insulated
state, hence we can account for the frequent occurrence of a plate presenting
parts of an image over its surface. It is quite evident that those parts ofplate's surface covered with moisture are nothing like as sensitive to theiodine as those parts perfectly free.

Exposure of the plate in the Camera, and Position.
The time of exposure necessary to produce an image upon the Daguerreotype plate,can only be determined by experiment, and requires a liberality of judgment tobe exercised on the part of the operator. The constant variation of the lightrenders it impossible to lay down any exact rule upon this point. Light is notalone to be considered; the amount of coating exercises a deviating influence,
also the subjects to be represented are not equally photogenic, some requiringmuch longer time of exposure than others. This may be easily observed byexposing the plate at the same time to a plaster bust and a piece of black
velvet, the first being a much stronger reflector of light than the latter: thetime necessary to produce a well developed image of the velvet being about six
times longer than that required to produce an equally defined image of plaster.
The manner of judging correctly of the time is by the appearance of impression
after it has been developed by the mercurial vapors. Should it present a deep
blue or black appearance it is solarized or over-timed. This sometimes is to an
extent, that a perfect negative is formed, the white being represented black,and the dark light.
An object requiring the particular care and attention of the operator is theproper focus. It is not unfrequently the complaint of sitters that their hands
are represented as being magnified and greatly out of proportion with thegeneral figure. This is the case also with the nose and eyes, but in a lessdegree. As this cannot be wholly remedied, it is desirous to come as near as
possible, and in order to do this, it is necessary to present the figure in sucha position as to bring it as nearly as possible upon the same plane by making
all parts nearly at equal distance from the lenses. This must be done by thesitter inclining the head and bust formed to a natural, easy position, andplacing the hands closely to the body, thus preserving a propel proportion, andgiving a lively familiarity to the general impression. It is not an uncommon
fault among our less experienced operators to give a front view of the face ofnearly every individual, regardless of any particular form, and this is often
insisted upon by the sitter,* who seems to think the truth of the picture exists
principally in the eyes staring the beholder full in the face.
Nothing, in many instances, can be more out of place in a Daguerreotype portrait
than this, for let a man with a thin, long, defeated-politician-face, be
represented by a directly front view, we have, to all appearances, increased thewidth of the face to such an extent as to reveal it flat and broad, losing the* I might here picture some curious scenes experienced by our operators Everyone is familiar with a certain class of our community whose ideas of theimportance of a free and easy position of the body are too closely confined withstays, attention to toilet, tightly fitting dress coats and the like, to admitof being represented as if nature had endowed them with least possible power offlexibility. To such we would suggest the following, to be well learned andretained in the mind while presenting themselves before the Daguerreotype camera"The experience of one who has often been Daguerreotyped, is, to let theoperator have his own way."characteristic point by which it would be the most readily recognized. The
method we should adopt in taking the likeness of such an individual as above,
would be to turn the face from the camera, so as to present the end of the noseand the prominence of the cheek bone equally distant from the lenses, and thenfocusing on the corner of the eye towards the nose, we cannot in many cases,
fail to produce an image with the lips, chin, hair, eyes and forehead in theminutest possible definition.
It should be the study of every operator to notice the effect of the lights andshades while arranging the sitter, and at the same time be very particular togive ease in the position.
No matter how successful the chemical effect may have been, should the image
appear stiff and monument-like, all is lost. "In the masterpiece, grace andelegance must be combined."
I will here use the words of another, which are very true:
So great is the difference in many faces, when inspected in opposite
directions, that one of the two views, however accurately taken, would notcommunicate the likeness--it not being, the usually observed characteristic
form. When the right view of the head is obtained, it is first necessary toconsider the size of the plate it is to be taken on, so as to form an ideaof the proportion the head should bear to it. The mind must arrange thesepoints before we commence, or we shall find everything, too large or too
small for the happy proportion of the picture, and the conveying of a justnotion of the stature. The work will have to be done over, and time
sacrificed, if this is not attended to. The adjustment of the head to thesize of the plate (as seen from the margin of the mat), is not to be taught:
everyone must bring himself, by scrutinizing practice, to mathematicalaccuracy; for something will be discovered in every face which can besurmounted only by experience.
The eye nearest the camera, in a three-quarter-face, is placed in the middleof the breadth of the plate; the chin, in a person of middle stature, in the
middle of the length, and higher according to the proportional height of theperson.

In regard to the proper elevation of the camera, it may be here stated that I
have found it best in taking portraits where the hands are introduced, to place
the camera at about equal height with the eyes of the sitter, in order to bring
the face and hands equi-distant from the tube. It will be found, if the above befollowed, that by attaching a string to the camera tube, and making a semicircle, that the face and hands of the sitter will occupy a corresponding
distance, and the consequence is that the impression will appear without thehands being magnified. It has been found that a person with a freckly face canhave as fine, fair, and clear an impression as the most perfect complexion; thismay be done by the subject rubbing the face until it is very red. The effect is
to lessen the contrast, by giving the freckles and skin the same color and thephotogenic intensity of the red and yellow being nearly the same, an impression
can be produced perfectly clear.
When a child is to be taken, and there are doubts of its keeping still, theoperation may be accelerated by placing it nearer the window bringing the screen
nearer, and placing a white muslin cloth over the head; this will enable you towork in one third of the usual time. Should the person move, or the plate become
exposed to the light, it may be restored to its original sensitiveness byplacing it over the quick, one or two seconds.
Developing the Daguerreotype.
After the plate has been submitted to the operation of the light, the image isstill invisible. It requires to be exposed to the vapors of heated mercury. It
is not absolutely necessary to apply artificial heat to the mercury to develop
the image, for fair proofs have been produced by placing a plate over the bathat the ordinary temperature of the atmosphere. This plan, however, requires along time and cannot be adopted in practice, even if it were advisable. The time
more usually required in developing the image over the mercurial vapors, isabout two minutes, and the temperature is raised to a point necessary to produce
the desired effect in that time. This point varies as indicated by different
scales, but for the ordinary scales it is not far from 90 deg. cen.
The mercury bath is accompanied with a centigrade thermometer, by which the heatis regulated. Those furnished by the manufacturers are not always correct, andit requires some experience to find the proper degree on the scale.
I would here remark that it is advisable, when placing the spirit lamp under thebath, to so arrange it that the position of applied heat should always be on thesame point, viz., should the heat be directly under the bulb containing thethermometer it would raise the mercury in the tube to the point marked, and thetemperature of that in the bath would be far below what it should be; hence itis (where time is followed for developing) that many failures occur. This isobserved more readily in the large baths made of thick iron, particularly upon
first heating. In practice I apply the heat as nearly as possible between thecentre of the bottom of the bath and the bulb containing the mercury tube. It isadvisable to keep the lamp lighted under the bath from the time of commencing in
the morning to the close of business at night. By this means you have auniformity of action, that cannot be otherwise obtained.
It is well known to the experienced Daguerreotypist, that different atmospheres
have a decided effect upon the mercury in developing the Daguerreotype. It will
require a greater degree of heat for one atmosphere than for another. Experiencealone determines this little difference.
In summer, on cloudy and stormy days, mercurial vapors rise more readily andquickly than in the temperature of autumn or winter. From 60 degrees upwards

towards the boiling point (660 deg.), the vapors of mercury rise in greater
abundance and collect in larger globules on cold surfaces.
For various reasons I prefer a high temperature and short exposure. It
accelerates the process. It renders the lights of the picture more strong andclear, while the deep shades are more intense. It gives a finer lustre to thedrapery. The solarized portions also are very seldom blue, especially aftergilding. If heated too high, however, the light parts become of a dead, chalky
white, and the shadows are injured by numerous little globules of mercury
deposited over them. Just the right quantity of mercury leaves the impression ofa transparent, pearly white tone, which improves in the highest degree ingilding. To mercurialize with exactness is a nice point. If there is reason tosuspect having timed rather short in the camera, reduce the time over mercury ina corresponding proportion. A dark impression will be ruined by the quantity of
mercury which would only improve a light one.
If practicable, it is most expedient that the plate be submitted to the actionof mercury immediately on coming from the camera. I have frequently, however,carried plates for miles in the plate-holders and after exposing in the camera,brought them back to expose to mercury, and obtained fair proofs; but for thereason before given, it is advisable to carry along the bath, and bring out the
impression on the spot.
It is sometimes the practice of inexperienced operators to take the plate off
the bath and examine the impression by solar light. This plan should beabandoned, as it is almost sure to produce a dense blue film over the shadows.
This I am led to believe is occasioned by the action of light on the yetsensitive portions of the plate, and made to appear only by subsequent exposure
to mercury, being equivalent to solarization.
There has been little said by our professors upon the subject of the position of
the plates while exposed to the mercurial vapour. Mr. Hunt, in referring to thissubject, says:
Daguerre himself laid much stress upon the necessity of exposing the plateto the mercury at an angle of about 45 deg.. This, perhaps, is the mostconvenient position as it enables the operator to view the plate distinctly,
and watch the development of the design; but beyond this, I am satisfied
there exists no real necessity for angular position. Both horizontally andvertically, I have often produced equally effective Daguerreotypes.

I presume from the last sentence of Mr. Hunt, that he has confined his
experiments to the smaller sized plates. Hence he may not have thought of theeffect of the vertical exposure of a large plate.
In America this is a subject of no little importance. When an impression is tobe developed upon a plate fifteen by seventeen inches, were we to use an angleof about 45 deg., it would be found to make a perceptible difference in theappearance of the image. By examining the wood tops of our baths as formerly
made, it will be found that there is a great variation in the distance from themercury to the different portions of the plate. By measuring one of these tops
for the size plate above mentioned, I find the distance to the nearest point
between the mercury and the plate, to be thirteen, and the middle point sixteen,
and the furthest point twenty-one and a half inches: by this we see that one
point of the plate is eight and a half inches further from the mercury than thenearest point; even this is not the variation there would necessarily be, were
we to adopt the angle of 45 deg. as urged by Daguerre.
Among our principal professors, the beveltop will not be found in use where thelarge plates are used. Should any one feel desirous to test more minutely theeffect produced by a bevel top bath, I would suggest to them to place a frame,
so constructed as to hold three sixth size plates, and fit it to the top of thebath, and so arrange it with openings that the plates may be placed, one at thenearest point of the mercury, the second midway, and the third to the greatest
distance, and by placing the plates over at one and the same time, theexperimenter will be enabled to judge if there exists a difference in thedeveloping. In speaking of the above, reference is had to baths to the ordinary
heights used by operators.
We will now proceed to examine the effect produced by mercurial vapor upon theplate at different lengths of exposure. In some investigations which I have madeupon the appearance of the Daguerreotype impressions when developed over mercury
at 90 deg. C. (194 deg. F.), the following was the result. Plates, coated andexposed to light in our usual manner of operating, produced on exposure of
1/2 minute, whole impression, deep blue.
1 minute, ashy and flat; no shadows; linen, deep blue.
1 1/2 minute, coarse and spongy; shadows, muddy; drapery, dirty reddish brown.
2 minutes, shallow or watery; shadows, yellowish; drapery, brown.
2 1/4 minutes, soft; face, scarcely white; shadows, neutral; drapery, fine darkbrown linen somewhat blue.
2 1/2 minutes, clear and pearly; shadows, clear and positive, of a purple tint;
drapery, jet black, with the dark shades slightly frosted with mercury.
2 3/4 to 3 minutes, hard and chalky; shadows, harsh; drapery, roughened, andmisty with excess of mercury.
The foregoing results will be found general.
There are numerous opinions among our operators in regard to the quantity of
mercury necessary for a bath. As regards this, I need only say, similar resultsoccur when two pounds or two ounces are used, but the quantity generally
employed is about a quarter of a pound. I am of the opinion that one ounce willanswer as well as a larger quantity. I know of no better proof in favor of asmall quantity than that presented in the following incident. Several years
since, an operator (Mr. Senter, of Auburn, N.Y.) of my acquaintance, wasrequested to go several miles to take a Daguerreotype portrait of a deceased
person. He packed up his apparatus and proceeded over a rough road for somedistance to the house where he was to take the portrait, and arranging his
apparatus, with all the expedition which the occasion required, after having
everything in usual order (as was supposed), he proceeded and took some ten or
twelve very superior impressions. They were fine, clear, and well developed.
After taking the number ordered, he proceeded to repack his apparatus, and tohis surprise, when he took up the bottle he carried the mercury in, he found it
still filled, and none in the bath, except only such particles as had adhered tothe sides, after dusting and being jolted for several miles over the rough road.
From this it will be seen that a very little mercury will suffice to develop
fine proofs. I saw some of the impressions referred to above, and they werecertainly well developed, and very superior specimens of our art.
Removing the Coating.
After the impression has been developed over the mercurial vapor, the next stepis to remove the sensitive coating. For this purpose the following solution isused:
Put about two ounces of hyposulphite of soda in a pint of water, which should
always be filtered before using. A convenient way of doing this is to have twobottles, and a large funnel with a sponge pressed into the neck of it; or, what
is better, some filtering paper folded in it. The solution in one bottle, thefunnel is placed in the other, and the picture held over it; when the solution
is poured on the plate, it runs from it into the filter, and is always ready foruse.
It is best that the washing be done immediately on the plate coming from themercury bath. If allowed to stand long with the coating on, it assumes a very
dark tint--as the operation of the light continues, though less active thanwhile exposed in the camera, and destroys that brightness which would otherwise
have been obtained. It is preferable to wash and gild a picture without it firstbeing dried; yet when there are doubts of its giving satisfaction, there would
sometimes be a saving by drying and getting the decision of the subject before
gilding, as this last injures the plate for another impression. First, lightyour spirit-lamp, then with your plyers take the plate by the lower right-handcorner, holding it in such a manner that the plyers will form in a line with theupper left-hand corner; pour on, slowly, the hyposulphite solution, slightly
agitating the plate, until all the coating is dissolved off; then rinse off withclean water, and if it is not to be gilded, dry by holding the plate
perpendicular with the bottom left-hand corner lowest, and applying the blaze ofthe spirit-lamp to the back, at the same time blowing gently downward on theface of the plate.
The hyposulphite solution should be often filtered through a sponge, and it willanswer for a great number of washings. Yet it is observed that the mercury
collects in this solution in small globules; these often come in contact withthe plate, causing white spots, which spoil the impression. They should be
guarded against, and the solution renewed. Again, in order to prevent streaks orscum on the surface of the plate, it is necessary that the coating should be
removed with a good degree of uniformity. I find in practice that thehyposulphite of soda in our market varies much as regards strength, andconsequently the rule to be adopted is to make a solution of sufficient strength
to remove the coating in about ten seconds. I am aware that it may be said that
this strong solution would have a tendency to injure the impression by
destroying in a measure the sharpness of outline. To meet this, it need only to
be said that the preventive is, to not let the solution rest on the surface ofthe plate for a longer time than is absolutely necessary, and then it should be
drenched copiously with water; hence a chemical action upon the image isprevented and the general operation facilitated. This plan is adopted by our
first operators with the greatest success.
If the operator should allow the hyposulphite solution to run over the plate
unevenly, it is quite likely that white or blue streaks would result. These it
is impossible to remove without injury to the impression. Some, in order toprevent this, breathe over the surface, thus moistening it and putting it in acondition to receive the solution with greater uniformity. The plate should bewell washed with water before gilding.
Gilding, or Fixing the Image.
The next process to be given is that for fixing the image on the plate. This isdone by precipitating a thin film of gold over the surface and is productive of
the most brilliant effect when prepared immediately after the plate has been
washed with water after the application of the hyposulphite solution, and before
the plate has been allowed to dry. When, however, the plate has been dried andallowed to stand for any time, before gilding, the hyposulphite wash should beapplied as at first, in order to destroy any chemical coating that may have been
formed on exposure of the plate to the air. For gilding the larger plates, wehave a gilding stand so constructed that the plate can be put on a perfectlevel. In practice, I prefer holding the plate with nippers, fastened at one
corner. Hold the plate in the same manner as in removing the coating; pour on
the gilding, newly filtered, until the surface is wholly covered, and with theblaze of the spirit lamp, at least three inches high, apply it to the back of
the plate, moving it about, that the surface may be heated with as much
uniformity as possible. Continuing this operation, the surface will generally
become covered with small yellow bubbles which soon disappear, leaving the image
clear and distinct.

It is advisable to make use of a lamp having a sufficiently strong flame to
produce the effect in a few minutes. If after a first heating, it is found thatthe impression can admit of a greater degree of intensity, it might be heated
anew; but that is seldom necessary, and often by trying to do too, well, theoperator, if he persists in heating certain parts of the plate, may find theliquid dry up just above the flame, and inevitably cause a stain*; or else theblacks are covered with a film, or even the coating of gold may suddenly
exfoliate, when small particles are detached from the plate. The impression isthen entirely spoiled, but the plate may be re-polished.
It is not unfrequent that the surface assumes a dark, cloudy appearance. This is
generally the best sign that the gilding will bring out the impression with thegreatest degree of distinctness. Soon, the clouds gradually begin to disappear,
and, "like a thing of life" stands forth the image, clothed with all thebrilliancy and clearness that the combined efforts of nature and art can
produce. When in the operator's judgment the operation has arrived at thehighest state of perfection, rinse suddenly, with an abundance of clean water,and dry as before described.
When an impression is dark, the gilding process may be longer continued; butwhen light, it should be gilded quickly, as lengthening the time tends to bleachthe impression and make it too white. The cause of this appears to be, that witha moderate heat the chlorine is merely set free from the gold, and remaining inthe solution, instead of being driven off, with its powerful bleaching,properties, it immediately acts upon the shades of the picture. A dark
impression can thus, by a low heat, long-continued, be made quite light. To
procure the best effect, then, heat suddenly with a large blaze, and judging it
to be at the maximum, cool as suddenly as possible.
When the hyposulphite of gold is used instead of the chloride, a less heatshould be employed.
Coloring Daguerreotypes.
Of all the so-called improvements in the Daguerreotype, the coloring is theleast worthy of notice. Yet the operator is often, in fact most generally,called upon to hide an excellent specimen under paint. I can conceive of nothing
more perfect in a Daguerreotype than a finely-developed image, with clearness oflights and shadows, possessing the lively tone resulting from good gilding. Such
pictures, however, are not always had, and then color may perform the part ofhiding the imperfections. We present the following method as given in Willat's
Manual:* This can be remedied, however, if it is immediately washed over with the same
solution that is on the plate, so that the surface shall not become cool;
continue for a short time to apply the lamp under, and agitate the plateslightly, and it will soon be free from all imperfections and give a fine clear
tone.

Daguerreotype portraits are now commonly met with beautifully colored; but
the coloring is a process requiring great care and judgment, and many good
pictures are spoiled in fruitless experiments. Several different methods ofcoloring have been proposed. The simplest mode appears to be that of using
dry colors prepared in the following manner: A little of the color required,very finely ground, is thrown into a glass containing water, in which a few
grains of gum arabic have been dissolved. After standing a few moments, themixture may be passed through bibulous paper, and the residue perfectly
dried for use. The principal colors used are Carmine, Chrome Yellow, Burnt
Sienna, Ultramarine and White; boxes fitted with sets of colors properly
prepared, may be obtained of the dealers, and include Carmine, White, Lilac,
Sky Blue, Pink, Yellow, Flesh color, Orange, Brown, Purple, Light Green,
Dark Green and Blue. With a few colors, however, all the rest may be madethus: Orange, by Yellow and Red; Purple, with Blue and Red; Green, Blue andYellow; Brown, with Umber, Carmine and Lamp Black; Scarlet, Carmine andLight Red. While it is true that a little color may relieve the dark
metallic look of some Daguerreotypes, it must not be concealed that thecovering of the fine delicate outline and exquisite gradations of tone of agood picture with such a coating, is barbarous and unartistic.
The prevaling taste is, however, decidedly for colored proofs, and thefollowing directions will assist the amateur in ministering to thisperverted taste, should he be so inclined. The coloring should commence withthe face, and the flesh tint must be stippled on (not rubbed) with a small
camel's-hair brush, beginning from the centre of the cheek, taking greatcare not to go over the outline of the face, and also not to have too muchcolor in the brush; the eyes and eyebrows must not be touched with color.
After the flesh color is applied, take a piece of very soft cotton and pass
it very gently backwards and forwards over the face, so as to soften down
the color, and then apply the carmine to give the required tint. For men,the darker tints should predominate, and for women the warmer. Very lighthair may be improved by a slight tint of brown, or yellow and brown,
according to the color. In coloring the drapery, the same care must be used.
No rules can be laid down for all the different colors required, and theamateur had better obtain the assistance or advice of some one accustomed tothe use of colors. A little white with a dash of blue or a little silver,
will improve white linen, lace, etc. The jewelry may be touched with gold or
silver from the shells, moistened with distilled water, and laid on with afine-pointed sable-hair brush.
Brilliants may be represented by picking the plate with the point of a pinor knife.

CHAPTER II
Coloring Backgrounds--Transparent ditto--Gilding Dissolvent Solution
for removing Specks--Solarized Impression--To Purify Water--Cleaning
Mercury--Adhesive Paper--Black Stain for Apparatus--Sealing Wax for
Bottles--Rouge--Rotten Stone--Potassa Solution--Hyposulphite
Solution--Substitute for do.--Gilding Solution--Solution forincreasing the Brilliancy of the Daguerreotype--Bleaching Solution;-Cold Gilding--Neutralizing Agents--Buff Dryer--Keeping Buffs inorder--Cleaning Buckskins--Reflector for taking Views.
To Color Backgrounds
To obtain a properly colored back ground is a matter of no little importance tothe Daguerreotype operator. I had nearly exhausted all patience, and tried theskill of painters to obtain a back-ground that would be suitable to my purpose;but all to no avail. At last I adopted the following method, and at a cost ofcoloring of twenty-five cents, can now produce a back-ground far more valuable
than those which had cost five dollars before.
Take common earth paint, such as is used in painting roofs; mix this with water
to about the consistency of cream; then to four quarts of this mixture add about
one pint of glue water (common glue dissolved in water, also about as thick as
cream). This last will cause the paint to adhere to the cloth, to which it isapplied with a common white-wash brush. By applying the brush on the coating
while it is wet, it may be so blended that not a line can be seen, and aperfectly smooth color of any shade can be obtained. The shade of color I use isa light reddish-brown. Tripoli, rotten-stone, or any earthy matter, may be
applied in the same manner.
Transparent or Invisible Background.--I give this as originally published in my
System of Photography, 1849:
Take a large woolen blanket with long nap, the longer and rougher it is thefiner will be the effect produced; stretch it on a frame of sufficient size,and suspend the frame at the centre of the upper end by a string fastened toa nail in the ceiling, from three to five feet back of the sitter. Having
arranged this, fasten another string to the side of the frame, and while theoperation is going on in the camera, swing the back-ground from right toleft, continuing this during the whole time of sitting, and you have a clear"transparent" back-ground, which throws the image out in bold relief, andrenders the surface of the plate invisible. If equaled at all it is only byatmospheric back-ground. I consider it to be the best ever known, and thinkit needs but to be tried to afford satisfactory proof that it is so.
Although used by few before, since the first edition of this work at least
two thirds of the operators have adopted its use; for any one can at once
understand the principle and the effect which it produces.

It may be added that a motion imparted to any back-ground where softness isdesired, produces an excellent effect.
Gilding Dissolvent.
To one quart of muriatic acid add as much oxide of iron (common iron rust) as it
will dissolve in two days. This may be done by putting in the oxide in excess.
It should be frequently shook, and when wanted for bottling it should be allowed
to stand in order to settle. When this is done the solution may be poured off,and reduced by adding to it an equal quantity of water; then it is ready foruse. This constitutes a gilding dissolvent now in our market.
Solution for Removing Specks.
There is probably no one cause of complaint so general as "what makes thoseblack specks?" There are several causes which produce them, and probably themost general are dust, rouge, or a spray of moisture on the plate. It this be
the case, there is no solution which can remove them, as they have prevented achemical action with the silver, and their removal would only expose the surfaceof the plate which in itself would afford a contrast with the impression.
Another and less dangerous source of these specks is organic matter contained in
the solution employed in dissolving the chemicals, or the water in washing. muchof the hyposulphite of soda in market contains a sulphuret, which, coming incontact with the silver surface, immediately causes oxidation. Such spots, aswell also as most all others found on the plate after it has been exposed in thecamera, can be removed by the following, solution: To one ounce of water add apiece of cyanide of potassium the size of a pea; filter the solution and apply
by pouring it on the surface of the plate. In all cases the plate should firstbe wet with water. Apply a gentle heat, and soon the spots disappear, leaving
the impression clear and free from all organic matter.
In the absence of cyanide of potassium, a solution of pure hyposulphite of soda
will answer as a fair substitute.
To Redeem, a Solarized Impression.
The Daguerreotype plate, prepared in the ordinary manner, should be exposed in
the camera a sufficient time to solarize the impression. Then, before it be
exposed to the vapor of mercury, expose it for a very brief period to the vaporof either chlorine, bromine or iodine. Then expose over mercury, as usual. I
have produced singularly interesting results by this process.
To Purify Water.
Filter the water well, and then add about three drops of nitric acid to thepint. This can be used as absolutely pure water, but I would recommend the useof distilled water as preferable.

Cleaning Mercury.
Make a small bag of chamois skin, pour in the mercury, and squeeze it throughthe leather. Repeat this several times, and filter by means of a funnel made of
paper, with a very small aperture, through which it will escape and leave theparticles of dust, or other substances, in the paper. A paper with a pinhole
through it will answer as well, and it is less difficult to make.
Adhesive Paper.
Take gum arabic, four ounces, put it in a wide-mouthed bottle and pour on water
about one-third above the gum. Add half ounce of isinglass, or fish glue, and asmall piece of loaf sugar. Let all dissolve, and spread over French letter
paper, with a brush or piece of sponge. If once spreading is not enough, performthe same operation a second time.
Black Stain for Apparatus.
Dissolve gum shellac in alcohol, or procure shellac varnish at the druggists',
stir in lampblack, and apply with a sponge or bit of rag. This will adhere tometal, as well as wood, and is used for the inside of camera, tubes, etc.
Sealing Wax for Bottles.
Melt together six parts rosin and one beeswax, and add a small quantity oflampblack; or, if red is preferable, add red lead. Common white wax is best, as
most chemicals act less upon it.
When bottles containing bromine are to be sealed, it is well to grease thestopper. This, however, only when the bottle is in frequent use, for if it were
to be sent by any conveyance it would be likely to fly out.
Rouge.
The method employed by Lord Ross is probably unsurpassed in the production ofrouge. He has given his process as follows:
I prepare the peroxide of iron by precipitation with water of ammonia, froma pure dilute solution of sulphate of iron; the precipitate is washed,pressed in a screw press till nearly dry, and exposed to a heat which in thedark appears a dull, low red. The only points of importance are, that thesulphate of iron should be pure, that the water of ammonia should be
decidedly in excess, and that the heat should not exceed that I havedescribed. The color will be a bright crimson inclining to yellow. I have
tried both potash and soda, pure, instead of water of ammonia, but after
washing with some degree of care, a trace of the alkali still remained, andthe peroxide was of an ochrey color, till overheated, and did not polishproperly.

Care should be observed to apply rouge in a dry state to the surface of theplate.
I would remark, that so far as my experience has gone, I consider good rouge
fully equal to any other polishing, material for the last or finishingpolishing; consequently I shall not take up my space in enumerating any of thegreat variety that find few advocates.
Why Rouge is to be preferred.
Because it burnishes better, and because it assists in fixing the layer ofgold, rendering it less susceptible of being removed in scales when heated
too much.

Rotten Stone.
Purchase the best ground rotten stone of the druggist, put a few ounces at atime in a wedgewood or porcelain mortar, with plenty of clean rain water.
This should have about forty drops of nitric acid to the quart. Grind well,and after letting the mortar stand two minutes, pour into a third. Afterremaining undisturbed eight minutes, finally pour off into a fourth tosettle. Rinse back the sediment in the second and third, and grind over witha new batch. Repeat the operation till you have all in the fourth vessel.
Let this stand several hours, and pour off the water very carefully. Set thedeposit in the sun, or by a stove to dry. When perfectly dry, pulverize, and
it is ready for use. With a little trouble you will obtain in this way amuch better article than can generally be bought of dealers. For the lastwashing, alcohol, or a mixture of alcohol and water, is preferable.

Potassa Solution.
The use of a solution of potassa in the preparation of the plate was suggested
in the early history of the Daguerreotype. It was thought to possess somepeculiar property for improving the tone of the impression. It is used formoistening the rotten stone in polishing the plate, and may be prepared byputting about an ounce and a half of alcohol in a close bottle, and add half astick of caustic potash. This will soon become of a deep red color. For use,
fill your small bottle, having a quill in the cork, with alcohol, and add a few
drops of the above, or enough to change it to a bright orange or saffron color.
A Substitute for the Hyposulphite Solution.
M. DAGUERRE recommends the use of a solution of salt water for removing thecoating off the plate. I found this of some service at one time during mytravels. My hyposulphite bottle got broke and its contents lost, so as only toleave enough for preparing gilding. I resorted to the use of salt solution, andfound it to answer well. Make a saturated solution of salt in water. First washthe plate with clear water; then immerse it in the saline solution, when it
should be agitated, and the coating will soon disappear. Another process with asalt solution of half the strength of the above is very interesting andeffectual. The plate having been dipped into cold water, is placed in a solutionof common salt, of moderate strength; it lies without being acted upon at all;but if it be now touched on one corner with a piece of zinc, which has been
scraped bright, the yellow coat of iodine moves off like a wave and disappears.
It is a very pretty process. The zinc and silver forming together a voltaic
pair, with the salt water intervening, oxidation of the zinc takes place, andthe silver surface commences to evolve hydrogen gas; while this is in a nascentcondition it decomposes the film of iodide of silver, giving rise to the
production of hydriodic acid, which is very soluble in water, and hence
instantly removed.
This process, therefore, differs from that with hyposulphite. The latter acts bydissolving the iodide of silver, the former by decomposing it. It is necessary
not to leave the zinc in contact too long, or it deposits stains, and in large
plates the contact should be made at the four corners successively, to avoid
this accident.
Gilding Solution.
To one pint of pure rain or distilled water add fifteen grains of pure chlorideof gold, and to another pint add sixty grains of hyposulphite of soda. Whendissolved, pour the gold solution into the hyposulphite by small quantities,
shaking well after each addition. The soda solution must not be poured into thegold, as the gold would be immediately decomposed, and the solution turn black,and be unfit for use.
Some operators add muriate of potash and other substances, but these do notpossess any advantage except in cases where it is necessary to bleach thesolarized portions of the impression, and when such is the case, chloride of
sodium (common salt) is probably as effective and is the most convenient. Add
about a teaspoonful to two ounces of the gilding.
Solution, for Increasing the Brilliancy of the Daguerreotype.
This solution will have the effect to thoroughly cleanse the surface of thegilded plate and excite a powerful influence on the general character of theimpression. To a solution of three ounces of water, in which is dissolved aquarter of an ounce of cyanide of potassium, add one teaspoonful of a solution
containing six ounces of water and half an ounce of each pure carbonate ofpotash, alum, common salt, gallic acid, sulphate of copper, and purified borax.
While the plate is wet, pour on a little, and heat it with a powerful blaze. The
effect will be quickly produced, in from three to fifteen seconds. Rinse anddry, as in the gilding.
Bleaching Solution.
Make a saturated solution of muriate of ammonia (sal ammoniac) in pure water,
and filter through paper. Reduce with an equal quantity of water when used. Whenthe linen or any other portion of the impression is badly solarized, after
removing the coating, rinse with water; then pour this upon the surface in thesame manner as the gilding solution. If the solarization be very deep, apply thelamp beneath, and warm the plate a trifle. Now pour off, and, without rinsing,
apply the gilding. The whole operation must be quickly performed, or thechlorine soon attacks the shades of the picture. When properly done, however,the solarized parts are restored to a clear, transparent white.
Electro, or Cold Gilding.
This process I have adopted, and it produces exceedingly beautiful impressions
for the stereoscope, adding a great charm to the pleasing effect of that
instrument. It also possesses a pretty and curious effect on views. It is easyof trial, and may be used by dissolving one gramme of chloride of gold in half alitre of ordinary water, and thirty grammes of hyposulphite of soda in anotherhalf litre of similar water; then pour the solution of chloride of gold intothat of soda, by little and little, agitating it exactly as in M. Fizeau's
preparation, of which there is but a variation.
When you wish to use it, pour some into a plate, or any other vessel of the samekind, sufficient to cover the proof; then, after having added to it a drop ofammonia, immerse the plate in it as soon as you take it out of the mercury-box,
after having wiped its back and edges, and agitate the mixture quickly fromright to left, so as to dissolve rapidly the coating of iodide of silver as
usual. As soon as the plate appears white, cease all rapid motion, but continue
to give it a slight undulating one; for if it were allowed to remain still for
only a few minutes, the proof would be clouded. By little and little, thesurface of the plate takes a yellow tint, which darkens more and more,
approaching to bistre. You stop therefore, at the color you wish; and when the
proof has been washed and dried, in the manner previously explained, it will befound to be fixed, without any stain, with a limpid surface, and an
extraordinary warm tone. If you were to augment the proportions of the ammonia
or chloride of gold, the operation would progress much quicker, but then the
middle of the proof would be always much clearer than towards the border. The
mixture may be used several times without being renewed. It does not, however,give such a beautiful color to the impression as when it is newly prepared. Bycommunicating to the vessel containing the solution a continual motion, theimpression, when once immersed, will be fixed. During that time, and while
attending to anything else, watch its color; and at the end of ten minutes or aquarter of an hour, take it out of the bath and dry it.
Agent for Neutralizing Bromine, Chlorine, and Iodine Vapors.
Aqua ammonia, sprinkled about the chemical or coating room, will soon neutralize
all the vapor in the atmosphere of either chlorine, bromine, or iodine. No
operator should be without, at least, a six-ounce bottle filled with ammonia. A
little of its vapor about the camera-box has a decided and happy effect. Burnt
coffee, pulverized, has also the property of destroying the vapors of the abovechemicals, as also almost any other agent employed about the Daguerreotype room.
Its deodorizing properties are such that if brought in contact with air filledwith the odor of decomposing meat, it will instantly destroy all disagreeable
smell. It can easily be used in the Daguerreotype room by placing a little of
the raw bean, finely pulverized, on an old plate, and roasting it over the
spirit-lamp.
Buff Dryer.
There are various methods for keeping buffs dry and free from dust. Some place asheet of iron against the wall at an angle sufficient to put a lamp between it
and the wall, and then let the buff rest against the top of the sheet. By thismethod the buff is for its full length close to the heated iron, and at the sametime exposed to the heated atmosphere and any dust that may be free. I would
recommend some arrangement by which the buff would be enclosed. I have found thefollowing to answer the purpose well, which is a box of sheet iron twenty inches
long, eight wide and five high, with one end left open and the other closed; thecover is made of the same material, with the edges bent over to go on and off.
There are several wires running through the centre of the sides, which it isnecessary to cover with cloth or paper to absorb all the moisture that may bemade by applying the heat, and the buffs are put in and taken out at the open
end. In order that the heat may be as nearly uniform as possible, an iron bar
one inch wide, eighteen inches long and one half inch thick, is so bent that thecentre is one quarter inch from the bottom of the box, and that at least two
inches of each end come in contact with the bottom; this being riveted on thebottom, and a lamp with a small blaze applied to the centre of the bar of iron.
This will constitute one of the best and cheapest buff dryers in use. It may besuspended from the wall by placing wires around it, or it may stand upon legs.
Perhaps a more convenient plan is to place it under the workbench in a similar
position to a drawer. One precaution is necessary: when first heating the dryer,
apply but a very gentle heat. This will prevent an accumulation of moisture,
which would otherwise pass off in steam, coming in contact with the buff, thus
causing a dampness. Another caution: never have the temperature of the air in
the heater more than ten degrees above that which surrounds it.
When wheels are used, they should be encased in a sheet iron or wood case. All
those made for our market are provided in this respect.
Keeping Buffs in Order.
This is one of the most important objects to arrest the attention of theoperator. Every buff is more or less liable to get out of order by dust fallingupon or coming in contact with the polishing powder employed in cleaning theplate. The edge of every plate should be thoroughly wiped and freed from any
material that may adhere while cleaning. I have adopted the following method,which proves highly successful:

Rub the buff leather, holding the face down, with the sharp edge of a pair ofshears or a piece of glass. This brings out any portion of the skin which may
have become matted from any moisture, and also takes out any substance imbedded
in it, and prevents it from scratching. Then, with a stiff brush, rub the buff
well, and it will be found to work well. This same process employ on wheels andhand buffs every morning, or oftener, as occasion requires.
Preparing Buffs.
Two of these are necessary. That part of the stick to be covered should be about
eighteen or twenty inches long, and three wide, and made crowning on the facefrom one end to the other, about one half inch. Before covering, these are to bepadded with two or three thicknesses of Canton flannel. The buff should not be
too hard, but padded with flannel, so that by drawing it over the plate, it may
touch across the surface. The only proper material for buffs is preparedbuckskin; and if prepared in a proper manner, this needs nothing but to betacked upon the stick. There are several varieties of wheels employed; the one
most generally adopted is Lewis' patent, which consists of several varieties ofwheels. Any operator can make a suitable wheel on the same plan of a turning
lathe.
To Clean Buckskins.
When the operator is compelled to purchase an unprepared buckskin, the following
is a good process for cleaning it: There is always in the buckskin leather thatis purchased, more or less of an oily matter, which is acquired in its
preparation, sometimes even amounting, to a third of its weight. The following
is the mode of ridding it of this noxious ingredient: Dissolve, in about six orseven quarts of filtered water, about five ounces of potash; when dissolved,
wash with the solution an ordinary buckskin; when it has been well stirred in
the liquid, the water becomes very soapy, owing to the combination of the potashwith the oily matters contained in the skin. Throw away this solution and use
some fresh water without potash and rather tepid; change it several times until
it remains quite limpid. Then gently stretch the skin to dry in an airy shaded
place. When thoroughly dried, rub it well between the hands. It thus becomesvery pliant and velvet-like.
Reflectors for Taking Views.
There have been excellent cameras introduced for taking views, but the time of
exposure, which is increased in proportion to the focal length, is considered an
objection; consequently many adhere to the old plan of using the speculum, or
rather, substitute a mirror. I now have one which I have used for several years
and find it equal to any article of the kind have ever tried. One is easily madeby a tin man, at a trifling expense. Procure a piece of best plate lookingglass, two and a half by five inches for a quarter, or four by eight for a halfsized camera; put a piece of pasteboard of the same size on the back, to protect
the silvering, and stick around the edge in the same manner as in putting up a

picture. Take a sheet of tin for the large size, or a half sheet for the other;place the glass crosswise in the centre; bend the ends of the tin over the edgeof the glass and turn them back so as to form a groove to hold the glass, andstill allow it to slide out and in. These ends of the tin must be turned out
flaring, that they may not reflect in the glass.
Have a tin band about an inch wide made to fit close on the end of the camera
tube; place it on, and taking the tin containing the glass, bring it to an angle
of forty-five degrees with the tube, extending nearly the whole length of theglass in front of the lenses; lap the loose ends of the tin on each side of thetin rim, and having your camera turned on the side to throw the view lengthwise,
arrange the exact angle by examining the image on the ground-glass. When you
have it exactly right, hold it while it is soldered fast to the band. Take out
your glass and stain the tin black, to prevent reflection.

CHAPTER III: CHEMICALS.
Bromine and its Compounds--Iodine and its Compounds--Chlorine and its
compounds--Cyanide of Potassium--Hyposulphite of Soda--Hyposulphiteof Gold--Nitric Acid--Nitro-Muriatic Acid--Hydrochloric Acid-Hydrofluoric Acid--Sulphuric Acid--Accelerating Substances--Liquid
Sensitives--Dry Sensitives, etc., etc.
Bromine.
An article so extensively used in the practice of the Daguerreotypic art as
Bromine, is deserving of especial attention, and accordingly every person should
endeavor to make himself familiar with its properties and applications.

History This element was discovered in 1826 by M. Balard, in the mother-liquor,or residue of the evaporation of sea-water. It is named from its offensive odor
(bromos, bad odor). In nature it is found in sea-water combined with alkaline
bases, and in the waters of many saline springs and inland seas. The salt
springs of Ohio abound in the compounds of bromine, and it is found in thewaters of the Dead Sea. The only use which has been made of bromine in the arts
is in the practice of photography. It is also used in medicine In a chemical
point of view it is very interesting, from its similarity in properties, and theparallelism of its compounds to chlorine and iodine.
Dr. D. Alter, of Freeport, Pa., is the only American manufacturer, and furnishes
all of the "American Bromine." Yet we understand much purporting to be of German
manufacture is prepared from that made in Freeport. This is done by individuals
in this city, who get well paid for the deception.
For the successful application of bromine as an accelerating agent, we areindebted to Mr. John Goddard of London, who at the time was associated with Mr.
John Johnson, now a resident of this city.

Preparation. The mother-liquor containing bromides is treated with a current ofchlorine gas, which decomposes these salts, setting the bromine free, which atonce colors the liquid to a reddish brown color. Ether is added and shaken withthe liquid, until all the bromine is taken up by the ether, which acquires afine red color and separates from the saline liquid.
Solution of caustic potash is then added to the ethereal solution, forming
bromide of potassium and bromate of potash. This solution is evaporated todryness, and the salts being collected are heated in a glass retort withsulphuric acid and a little oxide of manganese. The bromine is distilled, and iscondensed in a cooled receiver, into a red liquid.

Properties. Bromine somewhat resembles chlorine in its odor, but is more
offensive. At common temperatures it is a very volatile liquid, of a deep red

color, and with a specific gravity of 3, being one of the heaviest fluids known.
Sulphuric acid floats on its surface, and is used to prevent its escape. At zero
it freezes into a brittle solid. A few drops in a large flask will fill thewhole vessel when slightly warmed, with blood red vapors, which have a densityof nearly 6.00, air being one. It is a non-conductor of electricity, and suffers
no change of properties from heat, or any other of the imponderable agents. It
dissolves slightly in water, forming a bleaching solution.

Chloride of Bromine. This as an accelerating agent is by many considered
superior to the other Bromide combinations. It can be readily prepared bypassing a current of chlorine through a vessel containing bromine. A mixture oftwo parts muriatic acid and one of black oxide of manganese, should be put intoa flask having a bent tube to conduct the chlorine vapor into the bromine in
another vessel. This last vessel should also be supplied with a bent tube for
conducting the combined vapors with a third vessel or receiver. On theapplication of the heat from a spirit lamp to the bottom of the flask, a currentof chlorine gas will be disengaged, and pass into the bromine, when it readily
combines, and gives off a vapor, which, when condensed in the third vessel,
forms a volatile yellowish-red liquid. It is best, even at ordinary temperature,
to place the receiver in an ice bath. For manner of using, see farther on, underhead of Accelerators.
Bromides. A bromide treated with oil of vitriol, disengages chlorohyadic acid;but vapors of bromine are constantly disengaged, at the same time imparting abrown color to the gas. If the bromide be treated with a mixture of sulphuric
acid, and peroxide of manganese, bromide is only disengaged. A solution of abromide gives, with of nitrate silver, a light yellowish white precipitate ofbromide of silver, which is insoluble in an excess of acid, and readily
dissolves in ammonia. The precipitated bromide is colored by light like thechloride, but is immediately tinged brown, while the chloride assumes at first a
violet hue. The bromides, in solution, are readily decomposed and chloride being
set free, colors the liquid brown.
In the whole range of heliographic chemicals there is probably not anothercollection less understood and being so productive of interesting investigation
as the bromides.

Bromide of Iodine. M. de Valicours furnishes us with the best method for
preparing this mixture:
Into a bottle of the capacity of about two ounces, pour thirty or forty
drops of bromine, the precise quantity not being of importance. Then add,grain by grain, as much iodine as the bromine will dissolve till quite
saturated. This point is ascertained when some grains of the iodine remain
undissolved. They may remain in the bottle, as they will not interfere withthe success of the preparation.
The bromide of iodine thus prepared, from its occupying so small a space,can very easily be carried, but in this state it is much too concentrated tobe used. When it is to be employed, pour a small quantity, say fifteen
drops, by means of a dropping-tube, into a bottle containing about half anounce of filtered river water. It will easily be understood that the bromide
of iodine can be used with a greater or less quantity of water without
altering the proportion which exists between the bromine and iodine.

This article forms a very good dry accelerator, and is by some persons thoughtsuperior to all others, as it works with great uniformity, and is less liable toscum the plate in coating at high temperatures, or when the thermometer
indicates a heat above 60 deg.

Bromide of Potassium is prepared by mixing bromine and a solution of pure potass
together, and evaporating to dryness; it crystallizes in small cubes, anddissolves readily in water. This agent is extensively employed in the paper andglass processes.
Bromide of Lime. This the principal accelerator used in the American practice,and is the best of all dry combinations at present employed. There are manyreasons why the dry is advantageous; these are too familiar to repeat.
The bromide of lime may be produced by allowing bromine vapor to act upon
hydrate of lime for some hours. The most convenient method of doing this is
to place some of the hydrate at the bottom of the flask, and then put somebromine into a glass capsule supported a little above the lime. As heat isdeveloped during the combination, it is better to place the lower part of
the flask in water at the temperature of about 50 deg. F.; the lime
gradually assumes a beautiful scarlet color, and acquires an appearance very
similar to that of the red iodide of mercury. The chloro-iodide of lime may
be formed in the same manner; it has a deep brown color. Both thesecompounds, when the vapor arising from them is not too intense, have an odor
analogous to that of bleaching powder, and quite distinguishable fromchlorine, bromine, or iodine alone.

Farther on, I have given, in connection with accelerators, a process I adopt,
which is far less tedious and equally reliable.

Bromide of Silver may be formed by pouring an alkaline bromide into a solutionof nitrate of silver, in the shape of a white, slightly yellowish precipitate,
which is insoluble in water and nitric acid, but readily dissolves in ammonia
and the alkaline hyposulphites. Chlorine easily decomposes bromide of silver,
and transforms it into chloride.
M. Biot has expressed his opinion, that it is not possible to find any substancemore sensitive to light than the bromide of silver. This is true to a certain
extent, but in combination with deoxidizing agents, other preparations have adecided superiority over the pure bromide of silver.

Bromide of Gold is readily prepared by adding a little bromide to the brown goldof the assayers, and allowing it to remain some time under water, or assistingits action by a gentle heat. It forms a salt of a bright crimson color, but inits general properties is precisely similar to the chloride used in gilding.

Bromide of Magnesia is prepared in the same manner as bromide of lime. This
mixture is particularly adapted for hot climates, and is used in this country bysome few who regard its use as a valuable secret.
Bromide of Starch. This preparation is much used, but not alone. It is combinedwith lime by putting about one part in measure of starch to four of lime. It isprepared by adding bromine to finely pulverized starch, in the same manner as
bromide of lime. (See Accelerators.)
Experiments with Bromine.
a.
Place in a very flaring wine glass a few drops (say ten) of bromine, thenplace a small piece of phosphorus about one-twentieth of an inch indiameter. Place the latter on the end of a stick from five to ten feet inlength. So place it that the phosphorus can be dropped into the glass, andin an instant combustion giving a loud report will be the result.
b.

Expose a daguerreotype plate to the vapor of bromine, it assumes a leadengrey color, which, blackens by light very readily. Exposing this to mercury
will not produce any decided action upon the lights. Immerse it in thesolution of the muriate of soda, and the parts unacted upon by lightbecomes a jet black, while the parts on which the light has acted will bedissolved off, leaving a clean coating of silver. This will be a mostdecided black picture on a white ground.

c.

Expose an impressioned plate, that has been sufficient time in the camera
to become solarized, to the vapors of bromine, and the impression will befully developed and exhibit no signs of solarization. The exposure over thebromine most be very brief. Chlorine or iodine will produce the same
result. The latter is preferable.
Again, should the impressioned plate be exposed too long over the vapor ofbromine, the impression would be rendered wholly insensitive to themercurial vapor. Hence this method is resorted to for restoring thesensibility of the plate when there is reason to believe that the
impression would not be a desirable one; as, for example, if a likeness ofa child be wanted, and it had moved before the plate had been sufficiently
long exposed in the camera, the plate may be restored to its original
sensitiveness by re-coating over bromine, as above, thus saving the timeand labor of re-preparing the plate for the chemicals.

d.

If by accident (we would not advise a trial to any extent of this), you
should inhale a quantity of the vapor of bromine, immediately inhale thevapor of aqua ammonia, as this neutralizes the dangerous effect of thebromine vapor. every operator should be provided with a bottle of ammonia,
as a little sprinkled about the chemical room soon disinfects it of alliodine or bromine vapor, and also tends to facilitate the operation in thecamera.

Iodine.
History of Iodine. This is one of the simple chemical bodies which was
discovered in 1812 by M. Courtois, of Paris, a manufacturer of saltpetre, whofound it in the mother-water of that salt. Its properties were first studied
into by M. Gay Lussac. It partakes much of the nature of chlorine and bromine.
Its affinity for other substances is so powerful as to prevent it from existingin an isolated state. It occurs combined with potassium and sodium in many
mineral waters, such as the brine spring of Ashby-de-la-Zouche, and otherstrongly saline springs. This combination exists sparingly in sea-water,abundantly in many species of fucus or sea-weed, and in the kelp made from them.
It is an ingredient in the Salt Licks, saline, and brine springs of thiscountry, especially of those in the valley of the Mississippi. It is sparingly
found in fresh-water plants, as well also in coal, and in combination withnumerous other bodies.
Fermented liquors contain iodine; wine, cider, and sherry are more iodureted
than the average of fresh waters. Milk is richer in iodine than wine;
independently of the soil, with which it varies, the proportion of iodine inmilk is in the inverse ratio of the abundance of that secretion. Eggs (not theshell) contain much iodine. A fowl's egg weighing 50 gr. contains more iodine
than a quart of cow's milk. Iodine exists in arable land. It is abundant insulphur, iron, and manganese ores, and sulphuret of mercury: but rare in gypsum,
chalk, calcareous and silicious earths. Any attempt to extract iodine
economically should be made with the plants of the ferro-iodureted fresh waters.
Most of the bodies regarded by the therapeutists as pectoral and anti-scrofulous
are rich in iodine.
It is probably to the application of this body that we owe the discovery of thedaguerreotype. There is no record of the precise date when Daguerre commenced
experimenting with iodine, but by the published correspondence between him and
M. Neipce, his partner, it was previous to 1833. There is no doubt, however,that the first successful application was made in 1838, as the discovery wasreported to the world early in January, 1839.

Preparation. Iodine is mostly prepared from kelp, or the half vitrified ashes ofseaweed, prepared by the inhabitants of the western islands, and the northernshores of Scotland and Ireland. It is treated with water, which washes out all
the soluble salts, and the filtered solution is evaporated until nearly all the
carbonate of soda and other saline matters have crystallized out. The remaining
liquor, which contains the iodine, is mixed with successive portions ofsulphuric acid in a leaden retort, and after standing some days to allow thesulphureted hydrogen, etc., to escape, peroxide of manganese is added, and thewhole gently heated. Iodine distills over in a purple vapor, and is condensed ina receiver, or in a series of two-necked globes.

Properties. Iodine is solid at the ordinary temperature, presenting theappearance of dark-grey or purple spangles, possessing a high degree of metallic
lustre. It somewhat resembles plumbago, with which it is sometimes diluted,
particularly when it is fine. Operators should endeavor to secure the larger
crystals. It melts at 224.6 deg., forming a brown or nearly black liquid. It
boils at about 356 deg., and emits a very deep violet colored vapor. It gives
off a very appreciable vapor, sufficient for all purposes of forming the iodide
of silver on the daguerreotype plate, at a temperature of 45 deg. or even lower.
Iodine crystallizes readily. Every operator has found upon the side of the jar
in his coating-box, perfectly regular crystals, deposited there by sublimation.
Water dissolves but a small proportion of iodine, requiring 7000 parts of water
to dissolve one of iodine, or one grain to the gallon of water. Alcohol andether dissolve it freely, as does a solution of nitrate or hydrochlorate ofammonia and of iodides.
The density of solid iodine is 4.95; that of its vapor 8.716. It greatly
resembles chlorine and bromine in its combinations, but its affinities are
weaker. It does not destroy the majority of organic substances, and vegetable
colors generally resist its action. It combines with several organic substances,
imparting to them peculiar colors. It colors the skin brown, but the stain soon
disappears.

Chloride of Iodine is formed by passing chlorine into a bottle containing someiodine. This can be readily done by pouring one ounce and a half of muriaticacid upon a quarter of an ounce of powdered black oxide of manganese, and heatit gradually in a flask, to which is adapted a bent glass tube. This tube must
connect with the bottle containing the iodine, and the yellowish-green gas
disengaged will readily combine with the iodine, forming a deep red liquid, andthe operation is complete. The use of chloride of iodine will be referred to inconnection with the Accelerators.
Iodides. The iodide treated with the oil of vitriol, instantly produces aconsiderable deposit of iodine; and if the mixture be heated, intense violent
vapors are disengaged. The reaction is due to the decomposition of oil ofvitriol by iodohydric acid, water and sulphurous acid being formed, and iodine
set free. The iodides in solution are decomposed by chlorine, iodine being
precipitated, the smallest quantity of which in solution is instantly detectedby its imparting to starch an intensely blue color.
Iodide of Potassium.* This compound is easily made in the following manner:
Subject to a moderate heat a mixture of 100 parts of iodine, 75 of carbonate of* I shall present the preparation of only a few iodides, and such as are more
intimately connected with the Daguerreotype.

potash, 30 of iron filings, and 120 parts of water. This mass must be thoroughly
dried and then heated to redness; the resulting reddish powder is to be washedwith water, and the solution obtained filtered, and evaporated to dryness. It isfound that 100 parts of iodine yield 135 parts of very white, but slightly
alkaline, iodide of potassium.

Experiment. On projecting dry pulverized iodide of potassium into fused
anhydrous phosphoric acid, a violent disengagement of iodine takes place,attended by a transient ignition; fused hydrate of phosphoric acid liberates
iodine abundantly from iodide of potassium; this reaction is accompanied by thephenomenon of flame and formation of a considerable quantity of hydriodic acid.
Iodide of Mercury. For the preparation of iodide of mercury, Dublanc recommends
to cover 100 grms. of mercury with 1 kilogrm. of alcohol, to add 124 grms. of
iodine gradually in portions of ten grms., and agitating between each fresh
addition, until the alcohol becomes colorless again. After the addition of thelast 4 grms. the alcohol remains colored, the whole of the mercury having become
converted into iodide. The resulting preparation is washed with alcohol; it iscrystalline and of a hyacinth color.
Iodide of Silver. This compound is formed upon every plate upon which a
Daguerreotype is produced. The vapor of iodine coming in contact with the silver
surface, forms an iodide which is peculiarly sensitive to light.
The various colors produced are owing to the thickness of the coating, and the
maximum sensibility of the coating, as generally adopted, is when it assumes a
deep yellow, or slightly tinged with rose color.
This compound is largely employed in most photographic processes on paper, andmay be easily prepared by the following formula: By adding iodide of potassium
to a solution of nitrate of silver, a yellowish-white precipitate of iodide ofsilver is obtained, which is insoluble in water, slightly soluble in nitricacid, and soluble in a small degree in ammonia, which properties seem easily to
distinguish it from the chloride and bromide of silver. Chlorine decomposes it
and sets the iodine free, and chlorohydric acid converts it into a chloride. It
fuses below a red heat. Although the effect of light on the iodide is less rapid
than on the chloride, the former sooner turning black, assuming a brown tinge;
but when in connection with gallic acid and the ferrocyanate of potash, it forms
two of the most sensitive processes on paper.
Iodide of silver dissolves easily in a solution of iodide of potassium, and theliquid deposits in evaporation crystals of a double iodide.

Iodide of Gold. If a solution of potassium be added to a solution of chloride ofgold, a precipitate of iodide of gold takes place, soluble in an excess of the
precipitate. A little free potash should be added to combine with any iodidethat may chance to be set free by the chloride of gold.

Iodide of Lime is prepared by adding iodine to hydrate of lime (which will bereferred to farther on) until the mixture assumes a light yellow shade, whenwanted for combinations with accelerators, or to a dark brown when employed forthe first coating. This latter mixture has been sold in our market under thename of "Iodide of Brome."
Experiments with Iodine.
a.
Place a plate which bas been exposed in the camera over the vapor of iodine
for a very brief period, and it will present the appearance of theimpression having been solarized.
b.

Upon a Daguerreotype plate, from which an impression has been effaced byrubbing or otherwise, the picture may be made to reappear by merely coating
it over with iodine.

c.

Place in a vessel a little water, into which put the smallest possible
quantity of free iodine and add a little starch, and the liquid will
instantly assume a blue color. Advantage is taken of this fact in thelaboratory to detect the presence of iodine in liquids. The starch should
be dissolved in boiling water and allowed to cool. There are numerous otherinteresting experiments that can be performed by the aid of iodine, but it
is unnecessary here to consume more space.

Chlorine.

History.
The Swedish chemist, Scheele, in 1774, while examining the action ofhydrochloric acid on peroxide of manganese, first noticed this element. He
called it dephlogisticated muriatic acid. It was afterwards, by the French
nomenclaturists, termed oxygenated muriatic acid, conceiving it to be a compoundof oxygen and muriatic acid. This view of its notice was corrected by Sir H.
Davy (in 1809), who gave it the present name. In 1840-41, this gas vas employed
for accelerating the operation of light upon the iodized Daguerreotype plate.
John Goddard, Wolcott & Johnson, Claudet, Draper, Morse and others, were among
the first made acquainted with its use. Count Rumford, Ritter, Scheele, Seebert
and others, experimented with chlorine in regard to its effect when exposed tothe action of light in combination with silver. In 1845, M. Edward Becquerel
announced that he had "been successful in obtaining, by the agency of solar
radiations, distinct impressions, of the colors of nature."
On the 4th of March, 1851, Neipce, St. Victor, a former partner of DAGUERRE,
announced that he had produced "all the colors by using a bath of bichloride ofcopper, and that a similar phenomenon occurs with all salts of copper, mixed
with chlorine."Preparation.
This is easily accomplished by putting about two parts of hydrochloric(muriatic) acid on one of powdered black oxide of manganese, and heating it
gradually in a flask or retort, to which may be adapted a bent glass tube. A
yellowish-green gas is disengaged, which being conducted through the glass tube
to the bottom of a bottle, can readily be collected, being much heavier than theair, displaces it completely and the bottle is filled (which can be seen by thegreen color); a greased stopper is tightly fitted to it, and another bottle may
be substituted. In all experiments with chlorine, care should be taken not toinhale the gas!
Properties.
Chlorine is a greenish-yellow gas (whence its name, from chloros, green), with apowerful and suffocating odor, and is wholly irrespirable. Even when muchdiluted with air, it produces the most annoying irritation of the throat, withstricture of the chest and a severe cough, which continues for hours, with thedischarge of much thick mucus. The attempt to breathe the undiluted gas would befatal; yet, in a very small quantity, and dissolved in water, it is used with
benefit by patients suffering under pulmonary consumption.
Under a pressure of about four atmospheres, it becomes a limpid fluid of a fineyellow color, which does not freeze at zero, and is not a conductor ofelectricity. It immediately returns to the gaseous state with effervescence onremoving the pressure.
Water recently boiled will absorb, if cold, about twice its bulk of chlorine
gas, acquiring its color and characteristic properties. The moist gas, exposed
to a cold of 32 deg., yields beautiful yellow crystals, which are a definite
compound of one equivalent of chlorine and ten of water. If these crystals arehermetically sealed up in a glass tube, they will, on melting, exert such apressure as to liquefy a portion of the gas, which is distinctly seen as ayellow fluid, not miscible with the water which is present. chlorine is one of
the heaviest of the gases, its density being 2.47, and 100 cubic inches weighing
76.5 grains.

Chlorine Water.
This combination, which is used in conducting M. Neipce's process, can bereadily prepared by conducting the gas into a bottle containing distilled water.
One part water dissolves two parts of chlorine.
Chlorides.
The metallic chlorides are nearly all soluble in water; that of silver andprotochloride of mercury being the only exceptions. A metallic chloride, treatedwith oil of vitriol, disengages chlorohydric acid. Heated with a mixture ofperoxide of manganese and sulphuric acid, chlorine is given off, which is easily
recognized by its odor and other physical properties.

The chlorides dissolve in water; give with nitrate of silver, a white
precipitate, even in highly diluted solutions, becoming violet colored andfinally black when exposed to the light. The rapidity of the change of color is
proportioned to the intensity of the light. It is insoluble in nitric acid, but
readily soluble in ammonia; it fuses without decomposition, forming, when cold,
a tough, horny mass, and is reduced by hydrogen and by fusion with carbonate ofsoda, or with resin.

Chloride of Bromine. (See page 74.)
Chloride of Iodine. (See page 85.)
Chloride of potassium or Muriate of Potassa
Dissolve half an ounce of carbonate of potassa in water, and neutralize withmuriatic acid. Upon concentrating the solutions, cubic crystals will beobtained, having a taste similar to common salt. They consist of potassium andchloride, and when dissolved in water they may be regarded as muriate ofpotassa.
Chloride of Lime.
Mix half an ounce of slacked lime (hydrate of lime) with six ounces of water,
and conduct into this milk of lime, with frequent agitation, as much chlorine
gas as will evolve from two ounces of muriatic acid and half an ounce of blackoxide of manganese. The liquid clarifies by standing; may be regarded as asolution of chloride of lime, and must be protected from the air and light. It
may also be made without putting in the water with the hydrate of lime, by
merely passing the chlorine into the hydrate of lime. This last is by some usedin preparations for accelerating the operation of taking Daguerreotypes, butwhen used for this purpose it is in small quantities.
Chloride of Calcium.
To one part of water add two parts of muriatic acid, and add pieces of common
chalk until effervescence ceases; then filter through cotton cloth and evaporate
it by placing it in all earthen or porcelain dish, over a slow fire, to theconsistency of a syrup. When cooling, large prismatic crystals of chloride ofcalcium are formed. These must be quickly dried by pressing between folds ofblotting paper and kept carefully excluded from the air, as it readily attractshydrogen. For most daguerreotype purposes, the syrup may be at once evaporated
to dryness. This is frequently placed in the iodine coating box for the purposeof keeping the atmosphere dry. It is so easily made that every operator can
provide himself with it in a short time, and at little expense.
Chloride of Gold.
Is prepared by dissolving gold in aqua regia, a composition of one part ofnitric to two parts of muriatic acid. Gold foil is the best for our purposes;
coin, however, answers, in most cases, for the daguerreotype operator, as thealloy, being so slight is not noticed in the gilding process. When the latter isused, it will facilitate the operation to beat it out, forming a thin sheet, andthen cutting in small strips. Where purity is required, foil is better. The goldis placed in three or four times its own weight of the above acids. For thispurpose, an evaporating dish is best (a common saucer will do); a moderate heat
may be applied to favor the action. The mixture should be stirred often with aglass rod; care should be observed not to apply too much heat, for at atemperature of about 300 deg. the chlorine would be expelled and leave ametallic precipitate, which would require re-dissolving. Acid may at any time be
added if necessary to dissolve the gold, but it is advisable to add as little
excess as possible, as it would require more time to evaporate. After all thegold has dissolved, and the liquid assumes a deep red color, the solution shouldbe allowed to cool, being stirred nearly all the time. This salt is of areddish-brown color. It is rarely we find in our market good chloride of gold,
as common, salt is used for the bulk; and when the bottles are labelled "15
grains," "20 grains," nine-tenths do not in reality contain exceeding fivegrains of chloride of gold. The salt is mixed with the above solution when it iscooling, and gives bright yellow crystals, which some of our uninformed
operators conceive to be the best quality.

Chloride of Silver (Oxide of Silver)Take any quantity of silver coin or other silver, roll or hammer it thin; cut insmall pieces. This in order to save time. Put the silver in a glass or earthen
vessel (Florence flask is best); pour in nitric acid and water, about threeparts of the former to one of the latter. The operation of cutting up the silver
may be facilitated by applying a gentle heat. This blue solution consists ofoxide of silver and oxide of copper, both combined with nitric acid. Should theoperator wish a pure solution of silver, which, however, is not always used, hemay obtain it in the following manner:
To separate the two metals contained in the above solution from each other, putsome bright copper coins into the solution and set it aside in a warm place forthree or four days, occasionally giving it a circular motion. The separated
laminae are pure silver, which is to be digested with ammonia until it ceases tobe colored blue. The silver, after being washed and dried, is again dissolved innitric acid, and the liquid, diluted with water, is kept as solution, of silver.
Either of the above solutions (the one of oxide of silver and copper, and thepure silver solution) may be prepared for use by putting them in a bottle, witha quantity of water, and adding common fine salt, you obtain a white curdy
precipitate of chloride of silver. No matter how much salt is used, provided
enough be added to throw down all the chloride of silver. This solution should
be well agitated and then allowed to stand for a few minutes; thus the white
precipitate is in the bottom of the bottle. When the water has become clear,
pour it off with care, leaving the sediment behind, then add a fresh quantity ofclean water, shake, let settle, and pour off as before. Repeat the same forseveral times, and the excess of salt will disappear, leaving the white
precipitate, which may be drained of the water and dried in the dark, and kept
free from light and air.

Cyanide of Potassium.
This important article is worthy the undivided attention of every
Daguerreotypist. I here give Mr. Smee's process for its preparation. This isfrom that author's work entitled, "Electro Metallurgy," American edition:
The cyanide of potassium, so often alluded to while treating of the metallocyanides, may be formed in several ways. It may be obtained by heating to adull redness the yellow ferrocyanate of potash, in a covered vessel,
filtering and rapidly evaporating it. The objection to this method, however,is that without great care the whole of the ferrocyanate is not decomposed,a circumstance which much reduces its value for electro-metallurgy. By
boiling, however, the ignited residue with spirits of wine this difficultyis said to be overcome, as the ferrocyanate is absolutely insoluble in thatmenstruum, while the cyanuret, at that heat, freely dissolves, and is as
easily re-deposited on cooling.
There is, however, a much better process by which this salt may be formed,
viz. by simply transmitting hydrocyanic acid through potassium. Although themodes of making this acid are very numerous, there is but one which islikely to be employed on a very large scale, and that is its formation fromthe yellow ferrocyanate by means of sulphuric acid. This process isperformed as follows: any given weight of the yellow salt is taken anddissolved in about five times its weight of water; this is placed in a
retort, or some such analogous vessel, to which is then added a quantity ofstrong sulphuric acid, twice the weight of the salt, and diluted with threeor four times its quantity of water. A pipe is carried from the neck of theretort to the receiving bottle, which should be kept as cool as possible.
For small operations, those invaluable vessels, Florence flasks, answer
well: a bent tube being connected at one end to its month, the other passing
into the second vessel; heat should be cautiously applied by means of an
Argand lamp, a little vessel of sand being placed under the flask, whichhelps the acid to decompose the salt. Prussic acid is then generated andpasses through the tube to the recipient vessel, which is to be charged withliquor potassae.
When the potash is saturated, the operation is completed. The Germans
recommend a strong, alcoholic solution of potassa to be used in the second
vessel, for in this case, the hydrocyanic or prussic acid combines with thepotassa, forming a hydrocyanate of potassa, or, the water being abstracted,
the cyanuret of potassium, which spontaneously precipitates, on thesaturation of the fluid, the cyanuret, being insoluble in strong alcohol.
The ferrocyanate of potash may be considered as containing three equivalentsof hydrocyanic acid, two of potash and one of iron; but, unfortunately, we
can only obtain half the acid from the salt, owing to the formation of acompound during its decomposition which resists the action of the acid. The
decomposition of this salt taking 2 equivalents or 426 grains (to avoid
fractions) would afford 3 equivalents or 81 grains of hydrocyanic, or
prussic acid, capable of forming 198 grains of cyanuret of potassium, whilein the retort there would remain 384 grains or 3 equivalents of bisulphate

of potash, and 1 equivalent or 174 grains of a peculiar compound, said tocontain 3 equivalents of cyanogen, 1 of potassium, and one of iron
(Pereira). It is manifest that, but for this later compound, we might double
the quantity of hydrocyanic acid from the yellow salt.

The decomposition just described is the one usually received; but too muchreliance must not be placed on its accuracy, for the analysis of the several
compounds is too difficult for the results to be fully admitted. The residue
left in the retort speedily turns to one of the blues, identical with, or allied
to, Prussian blue. This is at best a disagreeable process to conduct, for thehydrocyanic acid formed adheres so strongly to the glass, that, instead of being
freely given off, bubbles are evolved suddenly with such explosive violence as
occasionally to crack the vessel. This may be remedied as far as possible by theinsertion of plenty of waste pieces of platinum--if platinized, so much thebetter, as that facilitates the escape of the gas. The heat should be applied toevery part of the vessel, and the flame should not be allowed to play upon one
single part alone. Large commercial operations are performed in green glass orstone-ware retorts.
Now for one word of advice to the tyro: Remember that you are working withprussic acid; therefore, never conduct the process in a room, the fumes
being quite as poisonous as the solution of the acid itself; moreover, havealways a bottle of ammonia or chlorine by your side, that should you havechanced to inhale more than is pleasant, it will be instantly at hand tocounteract any bad effects. It is stated by Pereira, that a little sulphuricacid or hydroferrocyanic acid passes to the outer vessel, but probably theamount would be of no consequence for electro-metallurgy, otherwise, it
might be as well to use a Woulfe's apparatus, and discard the salt formed in
the first vessel. To the large manufacturer it may be worth considering
whether some other metallo-cyanuret, formed in a similar manner to theferrocyanuret, might not be more advantageously employed, because theresidue of the process last described contains a large quantity of cyanogen
which the acid is unable to set free.
There are other modes of procuring prussic acid, besides the one which has
been so tediously described; but these are found to be more expensive. The
only one which I shall now notice is the process by which it is obtained
from bicyanide of mercury. The bicyanide of mercury itself is formed whenperoxide of mercury is digested with Prussian blue, the peroxide of mercury
abstracting the whole of the cyanogen from the blue, and leaving the oxides
of iron at the bottom of the vessel. The solution may be evaporated todryness, and one part of the salt dissolved in six of water; one part ofmuriatic acid, sp. gr. 1.15, is then added, and the solution distilled, when
the whole of the hydrocyanic acid passes over, and by being conducted into asolution of potassa, as in the former process, forms cyanuret of potassium.
This process, though easier than the first described, is rather given as aresource under peculiar circumstances than as one to be adopted by the large
manufacturer. The expense is the only objection, but in a small quantity
this cannot be a consideration.
In giving this very rough outline of the general mode of forming salts, theminutiae necessary for chemical work have altogether been avoided, and thoseparts alone are entered upon which are more immediately necessary for theelectro metallurgist to know and practice for himself. This will account for
the long description of the cyanuret of potassium, while the preparation of
the equally important and even more used acids, the sulphuric, muriatic,
etc., commonly found in commerce, are altogether neglected.
In using solutions of cyanide of potassium, the workman should not immerse
his arms into them, otherwise it occasionally happens that the solution
produces very troublesome eruptions over the skin.

Hyposulphite of Soda.
This salt forms one of the important chemicals for the Daguerreotype operator.
Its application to this art is of an interesting nature. It is used to dissolve
the sensitive salt of silver which remains unchanged during the exposure in thecamera. It has the property of readily dissolving the chloride, bromide andiodide of silver. It should be pure and free from sulphuret of sodium; should
this last be present, it will cause brown spots of sulphurated silver upon theDaguerreotype impression. This annoyance is a great source of complaint frommany operators, and ever will be, so long as it is prepared by men who have no
reputation to lose, and whose eyes are blinded by the "Almighty Dollar."
A good article may be prepared as follows:
Mix one pound of finely pulverized carbonate of soda with ten ounces offlowers of sulphur, and heat the mixture slowly in a porcelain dish till thesulphur melts. Stir the fused mass, so as to expose all its parts freely tothe atmosphere, whereby it passes from the state of a sulphuret, by theabsorption of atmospheric oxygen, into that of a sulphite, with thephenomenon of very slight incandescence. Dissolve in water, filter thesolution, and boil it immediately along with flowers of sulphur. The
filtered concentrated saline liquid will afford, on cooling, a large
quantity of pure and beautiful crystals of hyposulphite of soda.

Hyposulphite of Gold.
This compound salt is by a few considered preferable to the chloride of gold,
but our experience has induced us to use the latter, believing we are enabled to
produce a more brilliant and warm-toned impression with it. When thehyposulphite of gold is used in gilding, it requires less heat and a longer
application, as there is some danger of producing a glossy scum over some partsof the surface of the plate. I prepare this salt as follows:
Dissolve one part chloride of gold and four parts hyposulphite of soda in equal
quantities of distilled water: pour the gold into the hyposulphite solution, inthe same manner as in mixing the gilding solution; let it stand until it becomes
limpid; filter and evaporate to dryness. Re-dissolve and add a few grains ofburnt alum.

After standing a few hours, filter and evaporate again. If not sufficiently
pure, repeat the crystallization until it is so. For gilding, dissolve in waterand use in the same manner as the common gilding solution.
N.B.; The four following mixtures were employed in Neipce's process in his
earliest experiments:

Aqueous Solution of Bichloride of Mercury.
Eight grains of bichloride of mercury in 10,000 grains of distilled water.
Solution of Cyanide of Mercury.
A flask of distilled water is saturated with cyanide of mercury, and a certain
quantity is decanted, which is diluted with an equal quantity of distilledwater.
Acidulated White Oil of Petroleum.
This oil is acidulated by mixing with it one tenth of pure nitric acid, leaving
it for at least 48 hours, occasionally agitating the flask. The oil, which isacidulated, and which then powerfully reddens litmus paper, is decanted. It isalso a little colored, but remains very limpid.
Solution of Chloride of Gold and Platinum.
In order not to multiply the solutions, take the ordinary chloride of gold, used
for fixing the impressions, and which is composed of 1 gramme of chloride ofgold and 50 grains of hyposulphate of soda, to a quart of distilled water.
With respect to chloride of platinum, 4 grains must be dissolved in 3 quarts ofdistilled water; these two solutions are mixed in equal quantities.

Acids.
I shall not go into the preparations of the various acids employed in theDaguerreotype. This would be useless to the operator, as there are few, if any,that it would be advisable to prepare. It is only necessary for the experimenter
to be made acquainted with their properties, and this in order to prevent any
haphazard experiments, which are too common among operators. Any person who may
be desirous to try an experiment, should first study the agents he wishes to
employ. By so doing much time and money will be saved; while the searcher after
new discoveries would rarely become vexed on account of his own ignorance, or be
obliged to avail himself of the experience of others in any department ofscience.
Nitric Acid
Exists in combination with the bases, potash, soda, lime, magnesia, in both themineral and vegetable kingdoms, and is never found insoluble. It has the same
constituents as common air, but in different proportions. The strongest nitricacid contains in every pound, two and a quarter ounces of water. Pure nitricacid is colorless, with a specific gravity of 1.5, and boiling at 248 deg.. It

is a most powerful oxidizing agent, and is decomposed with more or lessrapidity, by almost all the metals, to which it yields a portion of its oxygen.
The nitric acid of commerce, is generally the article used by theDaguerreotypist. This usually contains some chlorine and sulphuric acid. It is
obtained by the distillation of saltpetre with sulphuric acid. It is employed in
the Daguerreotype process for dissolving silver, preparing chloride or oxide,
nitrate of silver, [the former used in galvanizing,] and in combination withmuriatic acid for preparing chloride of gold, used in gilding. It is also usedby some for preparing the plate.

Acidulated Solution.
This solution is used for cleaning the surface of the Daguerreotype plate. It
has the property of softening the silver, and bringing it to a state in which it
is very susceptible of being either oxidized or iodized, hence it contributes toincrease the sensibility of the plate. The proportions are to one drop of acidadd from 15 to 20 drops of water, or make the solution about like sharp vinegar
to the taste.
Nitro-Muriatic Acid.
Aqua Regia is a compound menstruum invented by the alchemists for dissolving
gold. It is composed of colorless nitric acid (aqua-fortis) and ordinary
muriatic acid; the mixture is yellow, and acquires the power of dissolving goldand platinum. These materials are not properly oxidized; it nearly causes their
combination with chlorine, which is in the Muriatic acid.
Hydrochloric Acid (Muriatic Acid)
This acid forms a valuable addition to the chemicals employed by the practicalDaguerreotypist. This acid is formed by acting upon common salt (which is
chloride of sodium) by concentrated sulphuric acid. The water of the acid is
decomposed, and its hydrogen combines with the chloride of the salt to form
muriatic acid, and this unites with the sulphuric acid to form sulphate of soda;
60 parts of common salt and 49 parts of concentrated sulphuric acid, afford, by
this mutual action, 37 parts of muriatic acid and 72 parts of sulphate of soda.
The muriatic acid of commerce has usually a yellowish tinge, but when chemicallypure it is colorless. The former is commonly contaminated with sulphurous acid,sulphuric acid, chlorine, iron, and sometimes with arsenic.
Muriatic acid, from the fact of the presence of the chlorine, is used in theDaguerreotype process for dissolving gold, and in combination with various
accelerators. Its presence can be detected by ammonia. A strip of paper dippedin this and waved to and fro will emit a thick white smoke if the acid vapor bein the atmosphere. The ammonia neutralizes the acid fumes. By reversing theexperiment we can determine whether vapor of ammonia be in the air, and also
deprive these suffocating and dangerous gases of their injurious properties, andremove them from the air. Every Daguerreotype operator should be furnished with,at least, a six ounce bottle of aqua ammonia. Its operation is very nearly thesame on bromine and iodine vapor.

Hydrofluoric Acid (Fluorohydric Acid).
This acid is used to form some of the most volatile and sensitive compounds
employed in the Daguerreotype. It is one of the most dangerous bodies toexperiment with: it is volatile and corrosive, giving off dense white fumes in
the air. It combines with water with great heat. At 32 deg. it condenses into acolorless fluid, with a density 1.069. It is obtained from decomposition offluorspar by strong sulphuric acid. It readily dissolves the silica in glass,and consequently cannot be kept in a vessel of that material. It is prepared andkept in lead. It is employed in accelerators on account of its fluorine.
One small drop on the tongue of a dog causes death. The operator who wishes touse it should pour some of the liquid for which he intends it into a graduate,
or other vessel, and then add the desired quantity of acid. If by accident anyof the spray should fall upon the skin, it should at once be copiously drenchedwith water.

Sulphuric Acid.
There are two sorts of this acid: one is an oily, fuming liquid; this is made in
Nordhausen, in Saxony, and is commonly called "Nordhausen sulphuric acid," oroil of vitriol. The other which is the kind used in connection with theDaguerreotype, is common sulphuric acid. It is somewhat thinner, and when
undiluted is not fuming. This acid may be obtained in a solid and dry state,called anhydrous sulphuric acid.
The common sulphuric acid is made by burning sulphur, which forms sulphurous
acid. To convert this into sulphuric acid and gain more oxygen, nitric acid,
which is rich in that body, is added. It forms a limpid, colorless fluid, of a
specific gravity of 1.8. It boils at 620 deg.; it freezes at 15 deg. It is acridand caustic, and intensely acid in all its characters, even when largely
diluted.
Its attraction for basis is such that it separates or expels all other acids,
more or less perfectly, from their combinations. Its affinity for water is suchthat it rapidly absorbs it from the atmosphere, and when mixed with water muchheat is evolved. It acts energetically upon animal and vegetable substances, andis a poisonous, dangerous substance to get on the skin. It is a powerfuloxidizing agent; hence its use in the galvanic battery, for which purpose it ismostly used by the Daguerreotypist. The fumes of this being so much more
offensive than nitric acid, the latter is sometimes used. It is also employed insome of the more sensitive accelerators.

Accelerating Substances.
Remarks on the Accelerating substances Used in the Daguerreotype.--I have now
arrived at a point in this work, where the eye of the Daguerreotype public will
intently search for something new. This search will prove in vain, at least sofar as regards those who have enjoyed and embraced the opportunities forstudying the principles of our art. Every experienced operator has in a degree
become familiar with the mechanical uses of all the agents employed, while I
fear but few understand the properties, and laws governing those properties,
which are so indispensable to produce an image impressed upon the silver
surface.
There are three substances which form the bases for producing a Daguerreotype;silver, iodine and bromine. Each forms a separate body which is indispensable tothe operators success as the art is now practiced in America. With these three,compounds of great variety are formed.
The silver surface is first thoroughly cleaned and freed from all organic
matter, then exposed to vapor of iodine, producing an iodide of silver. The
plate upon which is this salt, is again exposed to the vapor of bromine, forming
a bromo-iodide of silver, a salt also.
As most of the various accelerators are compounds of bromine, with either
chlorine or fluorine combination, they partake somewhat of the nature of theselatter, giving results which can be detected by the experienced operator. Thus
muriatic acid is added for its chlorine, which can generally be detected by theimpression produced, being of a light, soft, mellow tone, and in most cases
presenting a brilliant black to that colored drapery. Those who wish toexperiment with agents for accelerating substances, should first study to wellunderstand their peculiar nature and properties; as well, also, to endeavor tofind out what will be the probable changes they undergo in combination as anaccelerator. This should be done before making the experiments. From theforegoing it will be seen that numerous compounds are formed from the same
basis, and, consequently, it would be a waste of time and a uselessappropriation to devote more of our space than is necessary to give theprincipal and most reliable combination.
In America, the words "Quick" and "Quick Stuff," are more generally used for andinstead of the more proper names, "Sensitives," or "Accelerators," etc. As it
has by use become common, I frequently use it in this work.

Liquid Accelerator, No. 1.
This mixture was used by me in 1849, and is given as it appeared in my "Systemof Photography," published at the above date:
Take pure rain or distilled water, one quart, filter through paper into a groundstopper bottle, and add, for warm weather, one and a half ounce chloride ofiodine; or for cold, one ounce; then add one ounce bromine, and shake well. Now
with care not to allow the vapor to escape, add drop by drop, thirty drops ofaqua ammonia, shaking well at each drop. Care must be taken not to add more at atime, as it evokes too much heat. This mixed, in equal proportions with John
Roach's quick, forms an excellent chemical combination. For this purpose, takeone and a half ounce of each, to which add ten ounces water, for warm weather,or from six to seven for cold. Pour the whole into a large box, and it will workfrom two to four months. I am now using (l849) one charged as above which has
been in constant use for three months, and works uniformly well. The above isright for half or full size boxes, but half of it would be sufficient for aquarter size box.
Coat to the first shade of rose over iodine, change to a deep rosy red overquick, and black about one tenth the first.
I would not now recommend the addition of "John Roach’s quick," as I believeequally good results can be produced without it. This liquid is now used bymany, and is very good for taking views.

Lime Water Quick.
This mixture is more used at present than all the other liquids ever introduced.
It produced the most uniform results, giving the fine soft tone socharacteristic in pictures produces from accelerators containing chlorine. To
one quart of lime water (this can be had of any druggist) add one and a half
ounce of pulverized alum. This should be shook at intervals for twenty--fourhours; then add one ounce of chloride of iodine and three fourths ounce ofbromine.
Lime Water. This is easily prepared by putting lime into water, say a piece ofquick-lime about the size of an egg into one quart of water. This should be
shook occasionally for two or three days and allowed to settle, when the water
can be poured off and used.
Use. To one part of quick add six parts of water; coat to a light yellow overthe iodine, to a rose color over the quick, and recoat about one tenth. The
above coating may be increased or diminished, it matters not, so that there is
not too much, and the proper proportions are preserved. Some add to the above asmall quantity of magnesia, say about a teaspoonful to the quart of liquid.

Liquid Accelerator, No. 2.
The following was for a long time used by one of the first houses in the UnitedStates, and probably was one of the first liquids ever used. It produces a finetoned picture, but is not considered as sure as the lime water quick:
Take rain water one quart, add pulverized alum until it is a little sour to thetaste, and a small piece, say one half inch square, of magnesia. Filter throughpaper, and add chloride of iodine one half ounce, bromine sufficient to take it
up, which is a little less than half an ounce.
Charge with one of quick to six of water; coat over iodine to a soft yellow,
nearly, but not quite, bordering on a rose; over quick to a dark purple, or
steel, and back one sixth to one tenth.

Wolcott's American Mixture. Van Loan Quick.

This mixture was first formed and used by T. Wolcott & Johnson and gained greatcelebrity for its productions. I have now a bottle hermetically sealed that
contains about a half ounce of this mixture prepared in 1841 by John Johnson,
now a resident of this city, and the former partner of Mr. Wolcott. The
preparation of this mixture, as furnished by Mr. Johnson himself, is given as
follows:
One part of bromine, eight parts of nitric acid, sixteen parts of muriaticacid, water one hundred parts. This mixture should be allowed to stand forseveral days; it improves by age.
Use. A few drops say, 6 to 12, of this mixture, should be put into about 6
or 8 ounces of water; it will require frequent replenishing by the additionof a few more drops. The plate should be coated over the dry iodine to a redjust bordering on a slate. and then exposed to the mixture only sufficiently
long to change the color. If this is not done in less than six seconds it is
not strong enough. Re-coat over the iodine full one fourth as long as firstcoating.

This exceedingly volatile compound is difficult to control from its instability;
it is but little used. The impressions successfully produced by this mixture arevery brilliant, and possess a pleasing peculiarity.

Dry Sensitives.

Hydrate of Lime.
The operation by which water is combined with lime is called slaking. Take apiece of quick lime, common lime used in mortar, and immerse it in warm water
for about fifteen seconds; then place it in an iron or tin vessel. It will soon
begin to swell, evolving a great deal of heat and emitting steam, and soon falls
into a fine powder, hydrate of lime. This should be well stirred and allowed tocool, and then bottled in order to prevent it from giving off the hydrate andrecovering the carbonic acid from the atmosphere. The last is detrimental to its
use with bromine, and is one cause of the complaint that "it will not takebromine." The hydrate of lime should, not be dried over a heat, as has been
supposed by many, for in that case the hydrogen is expelled and it returns to acarbonate. It is advisable to cool it in a damp place like a ground cellar. Muchof the lime in our market will not, except it be quite damp, combine with thebromine. This is owing to impurities. Nothing is equal to oyster-shell lime,
which I use altogether.
Bromide of Lime.
In preparing large quantities of this, we adopt the following method: Fill afour-quart bottle about two-thirds full of hydrate of lime; pour into this about
one or two ounces of bromine; then shake well, add more of the bromine, shakewell and let it stand for a few hours, adding sufficient bromine to give it afine red color. It is better when kept in the large bottles, as it forms a more
perfect combination: in other words it improves by age.
Use: Coat over the iodine to a rose red and then over this mixture to a purple
or slate; recoat over the first about one fourth as long as first coating.

Gurneys American Compound.
Of this compound there are two combinations, one for use, when the temperatureof the atmosphere is above 65 or 70 deg., and the other at a lower temperature.
The first is called No. 1, the second No. 2.
No. 1 is prepared by placing hydrate of lime in a bottle, say to three quarts of
the hydrate of lime, add one ounce of pulverized burnt alum, and as muchchloride of lime as can be put on a quarter of a dollar, and from l5 to 30
grains of dry pulverized iodine, or enough to change the color of the hydrate oflime, to the slightest possible tinge of yellow. There had better be less thancarry the color to a deeper shade. The object of using the iodine is to form acompound with bromine that is not so volatile as the bromine itself. No matter
how little iodine is combined with the bromine, the vapors possess theirrelative proportion; hence, only enough iodine to prevent "flaring," or as it isoften termed a "scum-coating," is used. The iodine should be thoroughly combinedwith the lime, which will take about one or two days. Should add bromine thesame as in bromide of lime, until the compound assumes a light red color. Use;
Coat over the iodine to a bright yellow color, then over the compound, No. 1, to
red color, recoat over iodine, about one sixth as long, as the time occupied infirst coating.
No. 2 is prepared in the same manner as No. 1, except the addition of theiodine, which is omitted. Use; Coat over iodine same as above, except recoat
over the iodine about one fourth to one half as long as first coating.

Dry Quick No. 1. Bromide of Lime and Starch.
The following compound forms an excellent accelerator, and is used by many. It
is claimed for this preparation, that it will hold the bromine longer thanothers where starch is not employed. As regards this claim we do not think it
can be substantiated. Our experience in practice has led us to the conclusionthat there is no great difference as respects durability, but there is somelittle difference as regards the tone of the impressions produced by its use.
To one quart of hydrate of lime add one quart of finely pulverized starch. To
this mixture add bromine, until it assumes a deep yellow or pink color.
Starch may be added to any of the dry mixtures. Use. Coat over the iodine to a
deep yellow, then over this quick to a red color, recoat about one sixth of thetime of first coating.
I will here again remark, that the exact color of the coating is not essentiallyprovided a proper proportion is preserved.

I have never seen it stated, though it be a fact worthy of note, that a
proportionate time for coating over the iodine and accelerator, will not answer.
For example: if a plate exposed to the vapor of iodine be perfectly coated in
sixteen seconds, and then exposed to an accelerator, (not having iodine in its
combination) receives its coating in four seconds, it will be found that aproper proportionate coating cannot be preserved by adopting, a proportion oftime, but on the contrary, the time will diminish; for exposure over theaccelerator, as in the above example, if it be desired to coat the plate withtwice as much iodine as in the above example, the time would be, over iodine
thirty-two seconds, and over the accelerator (to possess a proper proportion)from six to seven seconds. Hence it is that many inexperienced operators, whenwishing to vary their usual manner of coating, fail in producing a favorable
result. They coat calculating a proportion of time when they should not.

Dry Quick, No. 2. Bromide of Lime and Magnesia.
To one quart of hydrate of lime add one quart of magnesia, and mix them welltogether; add bromine same as in preparing bromide of lime; coat the same asover dry quick No. 1. This combination produces very uniform results, and isworked with much success by beginners.
Chloro-Bromide of Lime.
To the bromide of lime add chloride of bromine until the mixture becomes a paleyellow color, resembling sulphur. It should be shook well, and enough of thechloride of bromine added to bring the compound to a deep blood red color. Use;
Coat over the iodine to a pink color, and then over the above to a red, or justchanging the color. It should be remembered that accelerators containing
chlorine do not admit of a great change of color of coating on the plate.
Iodide of Starch.
This mixture can be employed for coating over in warm weather, and prevent the
flashing resulting at high temperatures. It may be used the same as the iodide
alone. To six ounces of finely pulverized starch, add one fourth ounce of dry
iodine. Use; Same as the dry iodine alone.
The same combination may be made with lime, magnesia and other substances.

Concentrated Solution of Iodine for First Coating.
It may appear strange to some of our old operators that an aqueous solution ofiodine can be used for coating the plate and forming the iodide of silver. It
has long been a cry among most operators that it is impossible to succeed when
the iodine box contains dampness. Now this is a great mistake, and we will here
state that in all cases where dampness appears upon a properly prepared
Daguerreotype plate, it is the result of a different temperature of the metalfrom the air which surrounds it. Mr. Senter, of Auburn, was the first of ouroperators who used a solution of iodine for coating the plate, and we several
years since saw his results, which would rival the production of any otheroperator. A concentrated solution of iodine is prepared by putting into a common

bottle two thimblesful of hyposulphite of soda and a rather larger quantity ofiodine, so that there may be more than sufficient. Add to it about 40 ounces ofcommon water (heated to 60 or 70 degrees), by little and little, moving, thebottle to warm it, for fear of breaking. After shaking it a short time, thewater is rapidly and strongly colored. The solution should be poured into abottle with a ground stopper, and when cool used for iodizing.
A solution of sufficient strength can be made by moistening or just covering theiodine with water.

Chloride of Iodine as an Accelerator.
This is probably one of the best accelerators that can be used for coating theplate for taking views; it works too slow, however, to meet the wants of theoperating room, yet its use was formerly, for a long time, adhered to by some ofour best professors. In producing views with this, we are successful inobtaining well-developed impressions, with a depth of tone and richness ofappearance not to be met with in the productions of any other substances. I giveits use as furnished me by an old and experienced operator, and published in
Humphrey's Journal, vol. I. p. 180:
As the process of using chloride of iodine may be of interest to some of our
subscribers, I take pleasure in giving the following manipulation. To one
ounce of chloride of iodine add two ounces of water; place this mixture in a
coating-box, the same as quick stuff; coat the plate with dry iodine to alight yellow, or lemon color; then bring the coating to a deep pink over thechloride. The plate must be recoated over the dry iodine.

This combination has been very successfully used in one of our most extensive
establishments in this city, and the superiority of the pictures produced by it
was considered as an equivalent for the additional time required to bring out
the impressions.

Chlorine as an Accelerator.
I shall here refer to but a single experiment in which I employed chlorine gas
for coating the plate. I was provided with a retort, the neck of which was
fitted to the jar of my coating-box, through a hole drilled for its reception.
This was fitted perfectly tight in my coating-box. I placed some pure undiluted
bromine water and the agents necessary for producing chlorine gas (in small
quantity) in the retort. The result was that my first experiment produced an
impression completely solarized in all its parts by an exposure of four secondsof time, which would have required an exposure of twenty seconds to produce a
perfectly developed impression by the usual process.
Another trial immediately produced one of the finest toned impressions I eversaw, perfectly developed in one second of time.
My next two or three experiments proved total failures. I was unable to produce
even a sign of an impression. By accident my retort was broken, and not being ina locality convenient to obtain another, my experiments were necessarilysuspended.
My attention was not called to this subject again for several years, when I
noticed an account of some similar experiments by F. A. P. Barnard and Dr. W. H.
Harrington, the latter of whom is now of the firm of Dobyns & Harrington, of New
Orleans.
From reading this article, I found my own difficulties explained. Too much of
the chlorine gas was present in my coating jar. I would like to see some of ourenterprising operators investigate this combination.
It is a singular fact, that the vapors of bromine and chlorine combining upon
the iodide of silver, produce a more sensitive coating than when the two are
combined in solution, as in chloride of bromine solution. Those having
Humphrey's Journal at hand, can refer to vol. i. p. 142.

To use Bromine Water or other Accelerators in Hot Weather.
An excellent plan for using bromine water is as follows:
Fill a two-ounce bottle quarter full of it, and then fill the bottle with finesand, which serves to preserve a low temperature; then place the bottle in a
porous cup, same as used in the battery; fill this also with sand, and close theend with plaster of Paris. Place this in a coating-box, and it will be found toact with great uniformity and be quite permanent.
Bromide of Lime, another accelerator, can be used in the same manner, except it
is, only necessary, when a solid sensitive is used, to mix it with the sandwithout placing it in a bottle. This method is employed with great success by afew, who have regarded it as a secret worth keeping.
A Combination, requiring the Use of only One Coating-box.--It is often wonderedby beginners, why some solution requiring only one coating cannot be employed.
This can be done, but the results are not so satisfactory as when two or moreare employed. Such an accelerator may be produced by adding alcoholic solutionof iodine to a solution of chlorate of potash, until the latter will take up no
more of the former, and to each ounce, by measure of this solution, ten drops ofa saturated solution of bromide in water are added. The solution of chlorate ofpotash is made by diluting, one part of a saturated solution of the salt withten parts of water. The use of the chlorate is simply as a solvent of iodine.

Fats as Accelerators.
The use of fats, oils, or greasy substances, has been one of the most emphatic
prohibitions about the Daguerreotype plate. Yet it has been proved that its
presence in a small quantity upon the silver surface has the effect of reducing
the time of exposure in the camera from two-thirds to three-fourths. An
application may be made as follows: Pour sweet oil, or rub beef or mutton fat,on a common buff, which is free from all polishing powders. With this, buff awell-cleaned plate, and it will leave a scum, which should be mostly removed byusing another buff, which should be clean. Coat the plate in the usual manner,and the result will be a great reduction in the time of exposure in the camera.
The impression produced upon a plate so prepared presents, when coming from thevapor of mercury, a grey, scummy appearance, which, on the application of heatin gilding, does not improve; hence its use is not generally adopted.
We have instituted some investigations upon this subject, and in the present
volume, we shall not refer to it further. Those wishing to learn more fully theeffect of light upon organic substances will find Robert Hunt's "Researches on
Light" an invaluable work.

CHAPTER IV. LIGHT AND OPTICS.
Light--Optics--Solar Spectrum--Decomposition of Light-Light, Heat, and Actinism--Blue Paper and Color for
the Walls of the Operating Room--Proportions of Light,
Heat, and Actinism composing a Sunbeam--Refraction-Reflection--Lenses--Copying Spherical Aberration-Chromatic Aberration.
It is advisable that persons engaging in the Daguerreotype art
should have at least a little knowledge of the generalprinciples of light and optics. It is not the author's design
here to give a full treatise on these subjects, but he only
briefly refers to the matter, giving a few facts.
It has been well observed by an able writer, that it is
impossible to trace the path of a sunbeam through our atmospherewithout feeling a desire to know its nature, by what power it
traverses the immensity of space, and the various modifications
it undergoes at the surfaces and interior of terrestrial
substances.
Light is white and colorless, as long as it does not come incontact with matter. When in apposition with any body, it
suffers variable degrees of decomposition, resulting in color,
as by reflection, dispersion, refraction, and unequal
absorption.
To Sir I. Newton the world is indebted for proving the compound
nature of a ray of white light emitted from the sun. The objectof this work is not to engage in an extended theory upon thesubject of light, but to recur only to some points of moreparticular interest to the photographic operator.
The decomposition of a beam of light can be noticed by exposing
it to a prism. If, in a dark room, a beam of light be admitted
through a small hole in a shutter, it will form a white roundspot upon the place where it falls. If a triangular prism ofglass be placed on the inside of the dark room, so that the beamof light falls upon it, it no longer has the same direction, nordoes it form a round spot, but an oblong painted image of sevencolors--red, orange, yellow, green, blue, indigo, and violet.
This is called the solar spectrum, and will be readily
understood by reference to the accompanying diagram, Fig. 1.

To those who are unacquainted with the theory of light (and fortheir benefit this chapter is given), it may be a matter ofwonder how a beam of light can be divided.

This can be understood when I say, that white light is a bundleof colored rays united together, and when so incorporated, they
are colorless; but in passing through the prism the bond ofunion is severed, and the colored rays come out singly andseparately, because each ray has a certain amount of refracting(bending) power, peculiar to itself. These rays always hold thesame relation to each other, as may be seen by comparing every
spectrum or rainbow; there is never any confusion or
misplacement.
There are various other means of decomposing white light besides
the prism, of which one of the principal and most interesting to
the Daguerreotypist is by reflection from colored bodies. If abeam of white light falls upon a white surface, it is reflectedwithout change; but if it falls upon a red surface, only the red
ray is reflected: so also with yellow and other colors. The raywhich is reflected corresponds with the color of the object. It
is this reflected decomposed light which prevents thebeautifully-colored image we see upon the ground glass in ourcameras.

A sunbeam may be capable of three divisions--LIGHT, HEAT, andACTINISM; the last causes all the chemical changes, and is theacting power upon surfaces prepared to receive the photographic
image. The accompanying illustration, Fig. 2, will readily bringto the mind of the reader the relation of these one to another,and their intensities in the different parts of a decomposed
sunbeam.
The various points of the solar spectrum are represented in theorder in which they occur between A, and B, this exhibits thelimits of the Newtonian spectrum, corresponding with Fig. 1. Sir
John Herschel and Seebeck have shown that there exists, beyond
the violet, a faint violet light, or rather a lavender to b, towhich gradually becomes colorless; similarly, red light exists
beyond the assigned limits of the red ray to a. The greatest

amount of actinic power is shown at E opposite the violet; hence
this color "exerts" the greatest amount of influence in theformation of the photographic image.
(Blue paper and blue color have been somewhat extensively usedby our Daguerreotype operators in their operating rooms andskylights, in order to facilitate the operation in the camera. I
fancy, however, that this plan cannot be productive of as muchgood as thought by some, from the fact, that the light fallingupon the subject, and then reflected into the camera, is, coming
through colorless glass, not affected by such rays as may bereflected from the walls of the operating room; and even if itwere so, I conceive that it would be injurious, by destroying
the harmony of shadows which might otherwise occur.) The
greatest amount of white light is at C; the yellow contains lessof the chemical power than any other portion of the solar
spectrum. It has been found that the most intense heat is at theextreme red, b.
Artificial lights differ in their color; the white light ofburning charcoal, which is the principal light from candles, oiland gas, contains three rays--red, yellow, and blue. The
dazzling light emitted from lime intensely heated, known as theDrummond light, gives the colors of the prism almost as brightas the solar spectrum.
If we expose a prepared Daguerreotype plate or sensitive paper
to the solar spectrum, it will be observed that the luminous
power (the yellow) occupies but a small space compared with the
influence of heat and chemical power. R. Hunt, in his Researches
on Light, has presented the following remarks upon theaccompanying illustration:

If the linear measure, or the diameter of a circle which shall
include the luminous rays, is 25, that of the calorific spectrum
will be 42.10, and of the chemical spectrum 55.10. Such a seriesof circles may well be used to represent a beam from the sun,which may be regarded as an atom of Light, surrounded with aninvisible atmosphere of Heat, and another still more extended,
which possesses the remarkable property of producing chemical
and molecular change.
A ray of light, in passing obliquely through any medium of
uniform density, does not change its course; but if it shouldpass into a denser body, it would turn from a straight line,
pursue a less oblique direction, and in a line nearer to aperpendicular to the surface of that body. Water exerts astronger refracting power than air; and if a ray of light fallupon a body of this fluid its course is changed, as may be seen
by reference to Fig. 4.

It is observed that it proceeds in a less oblique direction(towards the dotted line), and, on passing on through, leaves
the liquid, proceeding in a line parallel to that at which itentered. It should be observed that at the surface of bodies therefractive power is exerted, and that the light proceeds in astraight line until leaving the body. The refraction is more or
less, and in all cases in proportion as the rays fall more orless obliquely on the refracting surface. It is this law of
optics which has given rise to the lenses in our camera tubes,
by which means we are enabled to secure a well-delineated
representation of any object we choose to picture.
When a ray of light passes from one medium to another, andthrough that into the first again, if the two refractions beequal, and in opposite directions, no sensible effect will be
produced.
The reader may readily comprehend the phenomena of refraction,by means of light passing through lenses of different curves, byreference to the following diagrams:--

Fig 5 represents a double-convex lens, Fig. 6 a double-concave,and Fig. 7 a concavo-convex or meniscus. By these it is seenthat a double-convex lens tends to condense the rays of light toa focus, a double-concave to scatter them, and a concavo-convex
combines both powers.
If parallel rays of light fall upon a double-convex lens, D D,
Fig. 8, they will be refracted (excepting such as pass directly
through the centre) to a point termed the principal focus.

The lines A B C represent parallel rays which pass through thelens, D D, and meet at F; this point being the principal focus,
its distance from the lens is called the focal length. Thoserays of light which are traversing a parallel course, when they
enter the lens are brought to a focus nearer the lens thanothers. Hence the difficulty the operator sometimes experiencesby not being able to "obtain a focus," when he wishes to securea picture of some very distant objects; he does not get his
ground glass near enough to the lenses. Again, the rays from an
object near by may be termed diverging rays. This will be better
comprehended by reference to Fig. 9, where it will be seen thatthe dotted lines, representing

parallel rays, meet nearer the lenses than those from the point
A. The closer the object is to the lenses, the greater will be
the divergence. This rule is applicable to copying. Did we wish
to copy a 1/6 size Daguerreotype on a l/l6 size plate, we should
place it in such a position to the lenses at A that the focus
would be at F, where the image would be represented at about theproper size. Now, if we should wish to copy the 1/6 size
picture, and produce another of exactly the same dimensions, wehave only to bring it nearer to the lenses, so that the lens D E
shall be equi-distant from the picture and the focus, i. e. from
A to B. The reason of this is, that the distance of the picturefrom the lens, in the last copy, is less than the other, and thedivergence has increased, throwing, the focus further from thelens."
These remarks have been introduced here as being important for
those who may not understand the principles of enlarging or
reducing pictures in copying.
I would remark that the points F and A, in Fig. 9, are termed"conjugate foci."
If we hold a double-convex lens opposite any object, we findthat an inverted image of that object will be formed on a paper
held behind it. To illustrate this more clearly, I will refer tothe following woodcut:

"If A B C is an object placed before a convex lens, L L, every
point of it will send forth rays in all directions; but, for thesake of simplicity, suppose only three points to give out rays,
one at the top, one at the middle, and one at the bottom; thewhole of the rays then that proceed from the point A, and fallon the lens L L, will be refracted and form an image somewhereon the line A G E, which is drawn direct through the centre of
the lens; consequently the focus E, produced by the convergenceof the rays proceding from A, must form an image of A, only in adifferent relative position; the middle point of C being in a
direct line with the axis of the lens, will have its image
formed on the axis F, and the rays proceeding from the point B
will form an image at D; so that by imagining luminous objects
to be made up of all infinite number of radiating points and therays from each individual point, although falling on the wholesurface of the lens, to converge again and form a focus or
representation of that point from which the rays first emerged,
it will be very easy to comprehend how images are formed, andthe cause of those images being reversed.
"It must also be evident, that in the two triangles A G B and D
G E, that E D, the length of the image, must be to A B, thelength of the object, as G D, the distance of the image, is to G
B, the distance of the object from the lens.
It will be observed that in the last cut the image produced by
the lens is curved. Now, it would be impossible to produce awell-defined image from the centre to the edge upon a plain
surface; the outer edges would be misty, indistinct, or crayonlike. The centre of the image might be represented clear andsharp on the ground glass, yet this would be far from the casein regard to the outer portions. This is called sphericalaberration, and to it is due the want of distinctness which isfrequently noticed around the edges of pictures taken in thecamera. To secure a camera with a flat, sharp, field, should be
the object of every operator; and, in a measure, thisconstitutes the great difference in cameras manufactured in thiscountry.
Spherical aberration is overcome by proper care in the formationof the lens: "It can be shown upon mathematical data that a lenssimilar to that given in the following diagram--one surface of
which is a section of an ellipse, and the other of a circle
struck from the furthest of the two foci of that ellipse-produces no aberration.
"At the earliest period of the employment of the camera obscura,a double-convex lens was used to produce the image; but thisform was soon abandoned, on account of the spherical aberrationso caused. Lenses for the photographic camera are now always
ground of a concavo-convex form,or meniscus, which corresponds more nearly to the accompanying
diagram."
Chromatic Aberration is another difficulty that opticians haveto contend with in the manufacturing of lenses. It will be
remembered, that in a former page (133) a beam of light isdecomposed by passing through a glass prism giving sevendistinct colors--red, orange, yellow, green, blue, indigo andviolet.
Now, as has been said before, the dissimilar rays having anunequal degree of refrangibility, it will be impossible toobtain a focus by the light passing through a double-convex lenswithout its being fringed with color. Its effect will be readily
understood by reference to the accompanying cut.
If L L be a double convex-lens, and R R R parallel rays of whitelight, composed of the seven colored rays,

each having a different index of refraction, they cannot be
refracted to one and the same point; the red rays, being theleast refrangible, will be bent to r, and the violet rays, being
the most refrangible, to v: the distance v r constitutes thechromatic aberration, and the circle, of which the diameter is al, the place or point of mean refraction, and is called thecircle of least aberration. If the rays of the sun are refracted
by means of a lens, and the image received on a screen placed
between C and o, so as to cut the cone L a l L, a luminous
circle will be formed on the paper, only surrounded by a redborder, because it is produced by a section of the cone L a l L,of which the external rays L a L l, are red; if the screen be
moved to the other side of o, the luminous circle will bebordered with violet, because it will be a section of the cone M
a M l, of which the exterior rays are violet. To avoid theinfluence of spherical aberration, and to render the phenomenaof coloration more evident, let an opaque disc be placed overthe central portion of the lens, so as to allow the rays only topass which are at the edge of the glass; a violet image of thesun will then be seen at v, red at r, and, finally, images of
all the colors of the spectrum in the intermediate space;consequently, the general image will not only be confused, butclothed with prismatic colors."
To overcome the difficulty arising from the chromaticaberration, the optician has only to employ a combination of

lenses of opposite focal length, and cut from glass possessing
different refrangible powers, so that the rays of light passing
through the one are strongly refracted, and in the other are
bent asunder again, reproducing white light.
To the photographer one of the most important features,
requiring his particular attention. is, that he be provided witha good lens. By the remarks given in the preceding pages, hewill be enabled, in a measure, to judge of some of the
difficulties to which he is occasionally subjected. We have inthis country but two or three individuals who are giving theirattention to the manufacture of lenses, and their construction
is such, that they are quite free from the spherical or
chromatic aberration.

CHAPTER V.
To make Plates for the Daguerreotype--Determining the Time of
Exposure in the Camera--Instantaneous Process for Producing
Daguerreotype--Galvanizing the Daguerreotype Plate--Silvering
Solution--Daguerreotype without Mercury--Management of Chemicals-Hints and Cautions--Electrotyping--Crayon Daguerreotypes--IlluminatedDaguerreotypes--Natural Colors in Heliography--Multiplying
Daguerreotypes on one Plate--Deposit in Gilding--Practical Hints on
the Daguerreotype.

To Make Plates For The Daguerreotype.
I do not give the method employed by our regular plate manufacturers; this is
not important, as the operator could not possibly profit by it from the fact of
the great expense of manufacturing. The following will be found practical:
Procure a well planished copper plate of the required size, and well polish it,
first with pumice stone and water, then with snake stone, jewelers' rouge.
Plates can be purchased in a high state of preparation from the engravers.
Having prepared the copper-plate, well rub it with salt and water, and then withthe silvering powder. No kind answers better than that used by clock-makers tosilver their dial-plates. It is composed of one part of well washed chloride ofsilver, five parts of cream of tartar, and four parts of table salt. This powder
must be kept in a dark vessel, and in a dry place. For a plate six inches byfive, as much of this composition as can be taken up on a shilling issufficient. It is to be laid in the centre of the copper, and the figures being
wetted, to be quickly rubbed over every part of the plate, adding occasionally alittle damp salt. The copper being covered with the silvering is to be speedilywell washed in water, in which a little soda is dissolved, and as soon as thesurface is of a fine silvery whiteness, it is to be dried with a very clean warm
cloth. In this state the plates may be kept for use. The first process is to
expose the plate to the heat of a spirit flame, until the silvered surface
becomes of a well-defined golden-yellow color; then, when the plate is cold,
take a piece of cotton, dipped in very dilute nitric acid, and rub lightly overit until the white hue is restored, and dry it with very soft clean cloths. A
weak solution of the hydriodate of potash, in which a small portion of iodine isdissolved, is now passed over the plate with a wide camel's hair brush. The
silver is thus converted, over its surface, into an ioduret of silver; and in
this state it is exposed to light, which blackens it. When dry, it is to beagain polished, either with dilute acid or a solution of carbonate of soda, andafterwards with dry cotton, and the smallest possible portion of prepared chalk:by this means a surface of the highest polish is produced. The rationale of thisprocess is, in the first place, the heat applied dries off any adhering acid,and effects more perfect union between the copper and silver, so as to enable it
to bear the subsequent processes. The first yellow surface appears to be anoxide of silver with, possibly, a minute quantity of copper in combination,
which being removed leaves a surface chemically pure.

Another Method.
The best and simplest mode with which we are acquainted is to divide anearthenware vessel with a diaphragm: one side should be filled with a very
dilute solution of sulphuric acid, and the other with either a solution offerroprussiate of potash, or muriate of soda, saturated with chloride of silver.
The copper plate, varnished on one side, is united, by means of a copper wire,with a plate of zinc. The zinc plate being immersed in the acid, and the copperin the salt, a weak electric current is generated, which precipitates the silver
in a very uniform manner over the entire surface.
Another Method.
A piece of brass or of polished copper, brass is preferred, is perfectly
planished and its surface made perfectly clean. A solution of nitrate of silver,
so weak that the silver is precipitated slowly, and a brownish color, on thebrass, is laid uniformlv over it, "at least three times," with a camel's hairpencil. After each application of the nitrate, the plate should be rubbed gently
in one direction, with moistened bitartrate of potassa, applied with buff. This
coat of silver receives a fine polish from peroxide of iron and buff. Proofs are
said to have been taken on it, comparable with those obtained on French plates.

M. Soliel's Process for Determining the Time of Exposure in the Camera.
M. Soliel has proposed the use of the chloride of silver to determine the timerequired to produce a good impression on the iodated plate in the camera. His
method is to fix at the bottom of a tube, blackened within, a piece of card, on
which chloride of silver, mixed with gum or dextrine, is spread. The tube thus
disposed is turned from the side of the object of which we wish to take theimage, and the time that the chloride of silver takes to become of a greyish
slate color will be the time required for the light of the camera to produce agood effect on the iodated silver.

Instantaneous Process for Procuring Daguerreotypes.
The following method of producing Daguerreotypes has by some been named asabove. Most experienced operators have been long acquainted with the effect ofthe vapor of ammonia upon the chemically coated plate. I will here insert Mr. W.
H. Hewett's plan of proceeding. This gentleman, in referring to it (published in1845), says:
This improvement consists in using the vapor of ammonia, as an object toaccelerate the action of light upon the plate. The effect is produced upon asimple iodized plate, but still more upon a plate prepared in the ordinaryway, with both iodine and bromine. By this means, the author obtained
impressions instantaneously in the sunshine, and in five to ten seconds in amoderate light; and he hopes to be able to take moving objects. It can beapplied by exposing the prepared plate over a surface of water, to which afew drops of ammonia have been added (sufficient to make it smell ofammonia); or the vapor can be introduced into the camera during the action.
In fact, the presence of ammonia, in the operating-room, appears to have agood effect, as it also neutralizes the vapors of iodine and bromine that
may be floating about, and which are so detrimental to the influences oflight upon the plate.

Galvanizing The Daguerreotype Plate.
In consideration of the importance of galvanized plates, I shall endeavor togive as plain and concise a manner of manipulation as possible. For some time it
was a question among the operators generally, as to the beneficial result ofelectrotyping, the Daguerreotype plate, but for a few years past our first
operators have found it a fact, that a well electro-silvered surface is the bestfor producing a portrait by the Daguerreotype.
From my own experiments, I have found that a plate, by being galvanized, can berendered more sensitive to the operation of the light in proportion of one tofive, viz.: if a plate as furnished by the market, be cleaned, polished, coatedand exposed in the camera, if the required time to freely develop an impression
be ten seconds, a similar plate prepared in like manner and galvanized, willproduce an equally well-defined image in eight seconds. In connection with thissubject, there is one fact worthy of notice; a plate with a very heavy coatingof pure silver, will not produce an equally developed image, as a plate with athinner coating, hence the thin coating, providing it entirely covers thesurface, is the best, and is the one most to be desired. The experiment is plain
and simple. Let the slate receive a heavy or thick coating by the electrotype,then polish, coat, expose in the usual manner, and the result will be a flat,
ashy, indistinct impression; when, on the other hand, the thin coating willproduce a bright, clear and distinct image, with all the details delineated.
The style of battery best for the purpose has been, and now is, a question of
dispute among operators; some preferring the Daniell battery to Smee's. Some
claim the superiority of the first from its uniformity of action; others, of thelatter, for its strength. I consider either good, and for the inexperienced
would prefer the Daniell. This is more simple in its construction, while it hascertainty in action. The more skillful electrotyper would prefer Smee's, andthis is the one most generally in use. I would remark that the plan ofgalvanizing plates should be followed by every operator, and when once
thoroughly tested, no one will abandon it.

Silvering Solution.
To any desired quantity of chloride of silver in water add, little by little,
cyanide of potassium, shaking well at each addition, until all the cyanide isdissolved. Continue this operation, and add the cyanide, until all the
precipitate is taken up and held in solution.
This solution is now ready for the plate-cup. Enough water may be added to cover
any sized plate when held perpendicular in the cup. The strength of the solution
may be kept up by occasionally adding the chloride of silver and cyanide ofpotassium. There should always be a very little excess of the cyanide.
The plate should be well cleaned and buffed, and the solution well stirred
before it is immersed. Care should be observed to keep the solution clean, andallow no particle of dust to come in contact with the surface of the plate. The
plate is now to be attached to the pole of the battery.
After remaining a short time, it assumes a blue color; take it out, rinse freely
with pure water, then dry with a spirit lamp, and it is ready for buffing. Buffand coat in the usual manner. Some operators are in the practice of immersing
the plate in the solution and buffing twice. This additional silvering is no
improvement wherever there has been a proper first coating.
Sometimes the operator is troubled with streaks or scum on the plate. This may
arise from three causes, all of which experience must teach the experimenter toavoid; first, too great an excess of cyanide in the solution; second, a lack ofsilver; third, the current too strong. Another annoyance arises from thesolution being dirty and the dirt collecting on the surface. When this is thecase, the dirt is sure to come in contact with the surface of the plate as it isplunged into the solution, and the result is a scum that it is difficult todispose of. This can be prevented only by frequent filtering. One thing should
always be borne in mind in electrotyping Daguerreotype plates--that in order tosecure a perfectly coated surface, the plate should be perfectly cleaned. In
this point, many who have tried the electrotype process have failed, attributing
their ill success to other than the proper cause.

Daguerreotypes Without Mercury.
The following process possesses some interest, and is worthy a trial fromoperators. M. Natterer, of Vienna, discovered a process for obtaining proofs on
iodized plates with the chloride of sulphur, without the use of mercury. A plateof silver is iodized in the usual manner, and then placed on the top of a vessel
six or eight inches high, having at the bottom, in a small cup, a few drops ofchloride of sulphur; it should remain exposed to the action of the vapor until
the sombre yellow color is changed to a red, after which it is brought to afocus m the camera, where it is exposed to the light in the camera, for about
the time necessary to produce an ordinary daguerreotype. The plate is then takenout and examined in the camera by the light of a candle. It often occurs that notrace of the image is as yet perceptible, but if the plate is heated by placing
over a spirit lamp the unprepared side, or if left for some time in the dark,or, lastly, if exposed only a few seconds to a weak, dimmed light, the positive
picture then appears with all its shades. Of these three modes of bringing out
the image, the second is superior to the others.

Management Of Chemicals.
It is necessary, first of all, to know that you have a chemical which is capableof producing good results when in skillful hands. For this reason it is best to
prepare your own quick, after some formula which is known to be good. Those
quick-stuffs which contain chloride of iodine are noted for their depth of tone
while they probably operate with less uniformity than those which are destituteof it. For operating under ordinary circumstances, especially with an inferior
light, probably no accelerator is more quick and sure than Wolcott's. It also
produces a very fine, white pleasing picture, though lacking that depth ofimpression so much to be desired. The dry quick operates with surety, and its
use is simple and easy, producing an impression much like Wolcott's. For thosehaving a good and permanent light, however, we would recommend a chemical giving
more body to the impression.
There is a class of accelerators called sensitives, claiming to work in fromthree to ten seconds, which, however, will be found very little, if any, moresensitive than this. We frequently work it with the ordinary coating in twelve
and fifteen seconds. The manner in which the sensitives are worked is by coating
very light. In this way, a flat, shallow picture is obtained in a few seconds;
and the same can be done with any of the more volatile quicks.
It is a fact not generally known, that a plate coated in a light chemical room
is more sensitive than when coated in darkness. By admitting a free, uniform
light, and exposing the plate to it a few seconds after coating, then timing
short in the camera, a very light, clear impression is obtained. The time in thecamera is reduced in proportion to the previous action of light. The shades, ofcourse, are destroyed, and the tone injured; still, for taking children, we havesucceeded better by this method than by the use of "sensitives." The discoveryof this principle was accidental, while operating where the direct ray s of thesun, entering the window just before sunset, fell on the curtain of our darkroom, rendering it very light within.
The selection of iodine is not unimportant. Reject, at once, that which hasanything like a dull, black, greasy appearance; and select that which is in
beautiful large crystalline scales, of a purple color, and brilliant steel
lustre.
Solarization, and general blueness of all the light parts of the picture, wereformerly great obstacles to success, though now scarcely thought of by firstclass artists. Beginners in the art, however, are still apt to meet with thisdifficulty. It is occasioned by dampness in the iodine box, which causes theplate to become coated with a hydro-iodide of silver, instead of the iodide. The

remedy is in drying your iodine. If in summer, you can open your box and set itin sunshine a few minutes; or if in winter, set it under a stove a short time.
The true method, however, is to dry it by means of the chloride of calcium. It
has such a remarkable affinity for water, that a small fragment placed in the
open air, even in the dryest weather, soon becomes dissolved.
Take one or two ounces of this chemical, heat it in the drying bath, or in a hot
stove, to perfect dryness; place it in a small glass toy dish, or large watch
crystal, and set it in the centre of your iodine box. Take this out and heat todryness every morning. Adopt this process, and with your mercury at a hightemperature, you will never be troubled with blue pictures.
Young operators are apt to impute all want of success in operating to theirchemicals, even though the cause is quite as likely to be elsewhere. Failure isquite likely to occur from dampness in the buffs, or in the polish; it istherefore necessary to be constantly on the guard in this quarter. With a viewto this, always scrape your buffs with a dull knife, or with one blade of yourshears, the first thing in the morning, and after brushing them thoroughly, drythem, either in the sun, by a stove, or in the buff-dryer. It is equallyimportant that the polish and the brush should be kept dry.
Want of success may arise from vapors of iodine or bromine in the camera box,
mercury bath, or even in the buffs. It is incredible how small a quantity ofthese vapors will affect the effect of light when coming in contact with theplate, after or during the exposure in the camera. It is therefore necessary to
be cautious not to mix chemicals, nor open your boxes or bottles in your room,
but take them out to do it. Never hurry the operation through from lack ofconfidence in the result. The fact of anything being out of order, forms no
excuse for slighting the process. If unsuccessful, do not pursue the same course
every trial, but vary with a view to detect the cause of the difficulty.
In case of a long series of failures, institute a regular course ofinvestigation, after this manner, commencing where the trouble is most likely tooccur:
1. Are the plates well cleaned?
2. Is the iodine dry? If the impressions come out blue, you may rest assured it
is not. Take out the iodine, wipe and dry the box, and dry the calcium.
3. Is the quick battery of the right strength? If dry, it must change the platein from six to fifteen seconds. If any of the chloride of iodine class, it mayvary from five seconds to a minute. Begin by coating light, and increase on eachtrial, observing the effect. If the light side of the picture seems loth to comeout, and shows no contrast with the dark side, it is to be inferred that yourbattery is too strong, and must be reduced with water or set out in the open air
for a few minutes, with the lid off. If working an old battery, never renew verystrong, or it will work dark and heavy. A battery, to work well, should begradually losing strength, but never gaining. An old battery, however, may bequickened up and made to work well for some time, by adding five of six drops ofsulphuric acid, repeating the quantity as often as necessary, providing always
that acid be not used in manufacturing the quick.
4. Have the plates lost their sensitiveness by being many times exposed tomercury? Clean and burn them; but if French plates, burn light, or you spoilthem.
5. Are the buff s dry and clean? Examine the plate critically after buffing todetect any appearance of scum or film on the surface. If so, the longer you buff
the more it shows. Scrape and dry the buffs thoroughly.
6. Is the mercury free from scum and dirt? If not, filter. Is it also far enoughfrom the coating boxes? Should be at least three feet, and kept covered.
7. Is the mercury sufficiently heated? This is important. Long exposure,
however, will answer the same purpose.
8. Are your lenses clean, and in proper place?
9. Are the tablets in focus with the ground-glass? If you can attribute thefailure to none of these, mix a new box of some other kind of quick, say thedry, for instance. If you fail in the same manner here, take time, wash yourbuffs, overhaul all the chemicals, and start anew. Do not be discouraged.
There is no day so dark but that the sun will shine again. We will close withthis brief summary of advice:
Clean your plates. Keep everything dry. Keep the mercury hot. Follow these
instructions carefully, and you must succeed.

Hints And Cautions.
First of all, cleanliness should be observed. When there is dust or dirt about
your room, particularly about the work-bench, failures will be frequent; for thesmallest particles of rotten-stone, when allowed to come in contact with thebuffs, will produce scratches on the surface of the plate, which very muchinjures the operation, and often causes failures.
Dust flying about the room is injurious, if allowed to fall on the plate, either
before or after it has been coated, as it causes black spots which cannot be
removed.
The polished plate should not be allowed to come in contact with a strong
current of air, for it tends to oxidize the surface. Breathing on the surface
should also be avoided, for the same reason.

The plate should, in all cases, be buffed immediately before using, and notallowed to stand any length of time. It should be held with the polished facedownward.
It is always best that the plate should be of the same temperature of theatmosphere in the room.
Keep the camera and mercury-bath perfectly free from the vapors of iodine andbromine; for the presence of the slightest degree of either of the above will
injure the impression in no small degree. As a preventive, let the camera be
exposed to the sun or fire for a few minutes in the morning.
Filter your mercury often, to keep the surface free from film and dust.
The hyposulphite solution should be filtered through sponge every time it isused.
The direct rays of light must not enter the camera in conjunction with thosereflected from the object; or the picture will be veiled, and the color of theplate changed to a thick green.
If the plate be iodized only to a light-yellow, the result might be of a bluishor grey tinge: and this is generally the case, when the quick is new and strong,
and there is an excess of it on the plate, and yet not enough to form thebromide iodide of silver; in which case it would wholly spoil the impression.
Your iodine will be found to operate more successfully, when the time requiredfor coating the plate does not fall short of fifteen seconds, or exceed one
minute.
Too quick coating can be avoided by using less iodine in your box. In the summer
months, when the weather is 80 deg. and over, one quarter of an ounce, or even
less, will work to advantage.

Electrotyping.
I am indebted to Mr. J. H. Fitzgibbons for the following process, which heemployed in producing the excellent specimens he exhibited at the Crystal
Palace:I shall endeavor to lay down in as comprehensive a manner as possible themethod by which I have been enabled to produce the most satisfactory
results. I use a Smee's battery (another kind will do). After filling thecell, of common size, nearly full with water; add about quarter of an ounceof sulphuric acid. Mix this well, and let it stand for about three hours, oruntil the action of the battery becomes weak, when it is in order to workwith a very uniform action. Put one pound of sulphate of copper in one quartof water; stir it until the sulphate of copper is all dissolved, and thenadd one half ounce of sulphuric acid and a quarter of an ounce of nitricacid. This solution, well mixed, should be filtered, and it is ready foruse. It is very important that the solution should be kept clean, clear, andfree from all foreign substance. The above quantity of this solution will befound sufficient for electrotyping a dozen of the sixth-size plates. When it
is required to be strengthened, it is only necessary to add a little of thesulphate of copper.
With the battery prepared as above, and the solution of sulphate of copper
in a vessel of proper dimensions to receive your plate, connect the galvanic
current, and immerse the impressioned plate, letting it remain until a thinfilm of copper has been formed, then the battery can be strengthened, andthe impression will be of sufficient thickness to be removed in from eight
to twelve hours. An old Daguerreotype plate attached to the opposite pole ofthe battery (copper side towards the face of the plate to be electrotyped),
will answer the same purpose as the silver-plate.
The great difficulty in taking an electrotype impression, and preserving theoriginal, has been attributed to the battery being too powerful. I am led tobelieve from practice that the principal difficulty has been in theDaguerreotype plate itself, for if we use an impression that has been taken
but a few days, and taken in the usual way, we will find it difficult tosucceed without spoiling both the copy and original, and so also with an old
impression.
I have found the most certain method to be as follows:--Coat theDaguerreotype plate as usual, except use less of the accelerators, theproportion of iodine coating being greater, of course the time of exposurein the camera will be lengthened. Mercurialize it at about a temperature
requiring to develop the image, from six to eight minutes, at least. Gilding
the Daguerreotype has much to do towards producing a good electrotype copy.
This should be done by applying a little heat, and gilding very slowly,
giving a coating of gold with the greatest possible uniformity. By thismethod, I have been enabled to produce any number of proofs. I have produced
a dozen from one impression, and it remains as perfect as when first taken.
By a little judgment and care the operator will be enabled to produce theelectrotype copy of the Daguerreotype plate without any difficulty. The
electrotype copy should be immediately put under a glass and sealed in thesame manner as the ordinary Daguerreotype.

Crayon Daguerreotypes.
This process is patented in the United States, by J. A. Whipple, of Boston, andof course no honorable person will use it for his own benefit without purchasing
a right.
A white back-ground is generally employed, the object being to blur the lower
portion of the plate, leaving the head of the subject in relief. Every
Daguerreotypist is familiar with the fact that a motion of any body between thecamera and the sitter will cause a "blur." Cut a piece of thin paper and scallop
it, making a semicircle. This is kept straight by means of a wire frame, and it
is to be moved in front of the lower part of the body of the sitter during thetime of exposure of the plate in the camera. Develop over mercury as usual, andthe result will be a crayon Daguerreotype.
Another method is to have a wheel with a hole cut through it of a diameter ofabout 12 inches. This hole is so cut as to leave teeth resembling those of alarge saw. This wheel is so arranged that it can be turned around, which should
be done during the time of exposure in the camera. It must be placed between thecamera and the sitter, and at such a distance from the camera as to allow suchproportion of the body of the sitter be seen upon the ground-glass as isdesired. It will be readily seen that by turning this wheel during the operation
will produce the same result as the paper being moved in the other method. The
teeth make the "blur." The side of the wheel towards the camera may be black, bywhich means the result will be a dark instead of a light border.

Illuminated Daguerreotypes.
This process is also patented, and the remarks on the preceding subject will
apply in this case. The plate is prepared and exposed as in the usual method of
the Daguerreotype. A white back-ground is employed. Let the head of the sittercome in the middle of the plate, and before exposing it to the vapors of
mercury, put a small mat or diaphragm, having a small hole through it, over ordirectly on the surface of the plate. This diaphragm should be bevelled, and thebevel should be towards the surface of the plate; this, in order to prevent too
sharp a line on the impression. It will be readily seen that if an impressioned
plate so covered is placed over the mercury, it will be developed on such
portions only as are exposed. The principle is so familiar that further
explanations are unnecessary.

Natural Colors In Heliography.
This subject is worthy the attention of every operator. The following process is
so plain and easy of trial that any Daguerreotypist can try it. This is as given
by Mr. James Campbell, and was published in Humphrey's Journal of theDaguerreotype and Photographic Arts, vol. 5, page 11. Mr. Campbell has done much
to further the process announced by M. Neipce, and his experiments have proved
highly successful.
The following is submitted as worthy of trial:
The proper preparation of the chloridated plate, to enable it to receive
colored impressions is an object of the first importance to those wishing toexperiment on it, and consequently requires particular notice. The plate may
be prepared by making it the positive pole of a battery, and letting it at
the same time be immersed in chlorine water. The negative pole should be aslip of platinum. All the colors may be produced from a plate so prepared if
the chlorine and water are in the right proportions; but generally one color
or the other predominates, according to the amount of chlorine in theliquid. By adding the chlorides of strontian, uranium, potassium, sodium,iron, or copper to the liquid, various effects may be produced, and thesebodies will be found to produce the same color on the plate that their flame
gives to alcohol.
The honor of this discovery is due to M. Neipce. Copper gives a variegatedflame; hence many colors may be impressed on a plate prepared with asolution of its chloride.
M. Neipce recommends a solution of the mixed chlorides of copper and iron,and it is with these, that I have been most successful. As the chlorides ofcopper and iron are not much used in the arts, they are not generally foundfor sale in the shops; and it may be well to furnish those not much versedin chemistry with an easy method of preparing them.
They may be made directly from either metal by dissolving it in hydrochloricacid; but they may be formed by a cheaper method, and by which also the acidfumes are avoided.
Sulphate of iron or copper, or both together, may be dissolved in water andthen neutralized with common crude potash, or its carbonate or bicarbonate-known commonly as pearlash and saleratus. If either of the latter be used,
there will be formed sulphate of potash and a carbonate of the metal used,
and there will also be a considerable effervescence of carbonic acid, which
will, if care is not taken, cause the mixture to run over the vessel. Afterthe copper or iron salt is neutralized, which is known by its ceasing toeffervesce, the carbonate of the metal will settle slowly, and will at firstnearly fill the vessel. The supernatant fluid, which is sulphate of potashin solution, may now be carefully poured off, and its place filled withwater; this operation should be repeated several times until the water which
passes off is tasteless. The carbonate of the metal rapidly changes to anoxide by contact with the air, and it will generally be found, when it issufficiently washed, that it is at least half oxide. On adding hydrochloric
acid cautiously to the mixture, a chloric of the metal will be formed, andcarbonic acid will be evolved from the remaining carbonate. The chloride
formed is soluble; but as there are two chlorides of these metals, and wewish to produce the one which contains the most chlorine, it is best to add
the acid cautiously until the solution is decidedly acid. After filtering
the solution, it is fit for use; and it should be preserved in wellstoppered bottles. The water used should be rain or distilled water.
About one part of the mixed chlorides should be used to three or four ofwater.
The battery may be either Smee's, Daniell's, or Grove's; if of either of theformer, it should be of two series; if of the latter, one cup is sufficient.
The plate on being immersed in the liquid, almost instantly takes a violet
color. It should be allowed to remain from two to five minutes, according to
the strength of the battery, and until it becomes nearly black. It shouldnow be carefully washed, and afterwards heated over a spirit lamp until ittakes a cherry-red color, and it is then ready for exposure in the camera.
Before speaking of exposing the plate, it may be well to speak of somedifficulties which the inexperienced operator may find in preparing it. If
the battery is not in good order, and a sufficient current is not passed
through the solution, the plate will become coated--and apparently almost as
well as when the battery is working well--but on exposure it will give anegative picture, and but little colored; while if the battery is in goodorder, the impression is invariably positive.
Sometimes on heating the plate after washing, the surface is covered withspots or assumes a variegated appearance. This indicates that the solution
is impure, or that the plate have not been thoroughly washed and are stillcontaminated with the soluble chlorides which are contained in the solution.
From the fact that the plate if prepared with positive electricity gives a
positive picture, while it prepared otherwise it gives a negative, it isevident that electricity plays an important part in this process. The sameis true to some extent with the compounds formed with iodine, bromine. andfluorine.
On heating the plate, the brown coating of chloride melts into a translucent
enamel, and the heat should be withdrawn when a cherry-red color is
produced. It the heat is continued longer, the plate assumes a lighter
color, and becomes less sensitive; and the enamel will finally scale off. To
produce a picture by the ordinary process of M. Neipce, unaccelerated, itshould be exposed for from three to five hours to sunlight in the camera,
though pictures may be procured by contact, in from fifteen to thirty
minutes.

Multiplying Daguerreotypes On One Plate.
I have produced some interesting specimens of the Daguerreotypic art, by
exposing in the camera only a portion of the sensitive plate to the action oflight. When on the exposed portion an image is formed, then taking the tablet
into the dark room, change ends and expose the sensitive portion, and produce
another image, developing as usual. This plan is adapted for taking likenesses
for lockets. Two images can be presented as sitting side by side, by covering
half the plate with black paper, and exposing as before. In this manner we havebeen enabled to surprise persons by exhibiting their portrait on the same platewith a stranger's. Daguerreotypists must be cautious in practicing this, as it
might not be agreeable to the parties whose likenesses are together, by theabove process. It is impossible to produce an impression without a line being
seen where the edge of the paper prevented the operation of the light.
I have recently seen a fine specimen produced by another plan, which far exceeds
the above, there being no line, or any peculiarity denoting two exposures. The
specimen referred to, was a gentleman represented on one plate by two fulllength portraits. This was produced by using a black velvet for the background.
The plate was exposed sufficient time to produce one impression, and then the

gentleman assumed another position, and is repeated as looking at himself. From
the fact that the time required to develop black velvet being so much longer
than that for producing a portrait, we are enabled to produce the above
interesting results.

Deposit In Gilding.
Regarding specks from bad water, I would remark that gilding should be made onlywith distilled water. Thus made, it produces very little deposit, even by longkeeping. It therefore preserves its original strength, and works with great
uniformity.
Every grain of deposit contains at least 7-10 its weight of gold, easily
discoverable by the blowpipe. Such gilding is continually deteriorating, whichwith good chloride and distilled water may be prevented. Distilled water should
also be used for the hyposulphite. and for cleaning plates. Any good, clear
water may be afterwards used for washing off, with equally good results. I amvery rarely troubled with specs, and deem this as the main reason.
With a portable still attached to a cooking stove, I obtain half a gallon ofwater per hour, and with very little trouble. A small tin retort or stillconnected with a Leibig's condenser, would not add much to the "traps" of thetravelling operator, and save him many a disreputable specimen.--T. J. BAILEY.-Humphrey's Journal.

Practical Hints On The Daguerreotype.
The following is from Humphrey's Journal, vol. 5, and from the pen of Dr. WM.
HARRINGTON, one of the most able writers upon the subject of the Daguerreotype
in this country:
THE CAUSE OF THE DIFFICULTY THAT SOMETIMES OCCURS TO PREVENT THE PRODUCTION OF A
CLEAR IMPRESSION UPON A DAGUERREOTYPE PLATE.
Beyond all doubt this is traceable to dampness. Truly this is not a new thought;
but where does this dampness come from? How does it originate, and where is it
located? Generally it has been referred to a point entirely remote from its real
location.
This dampness exists particularly upon the surface of the plate; is obviously
derived immediately from the atmosphere; and is owing to a certain relative
temperature of the plate with the hygrometric condition of the atmosphere.
Whenever this relation exists between the plate and atmosphere, a precipitationof moisture takes place upon the surface of the plate, which render all efforts
at polishing impracticable. This interference is not confined to the buffing

operation alone, but sometimes is discoverable even in the ordinary process ofscouring. Every one at all experienced in this art will remember that it is notalways an easy matter for him, by scouring, to bring his plate to the desired
lustre. All his efforts become unavailing; the more he rubs, the duller thesurface of his plate appears; and although he renews his cotton repeatedly,
still he is obliged to content himself with an unsatisfactory finish.
This relative condition is not confined to any particular season of the year,
nor to any certain thermometric temperature; but may occur in summer as well as
in winter; the weather being warm or cold, wet or dry, clear or cloudy, rainingor shining. Under any of these circumstances, if the relation of the plate andatmosphere be such as to invite upon the plate a precipitation of humidity fromthe atmosphere, the prospect of producing a clear impression is quite
problematical.
It is reasonable to expect this occurrence from the fact that metal is a goodradiator, and radiation reduces the temperature of a metallic body below that of
the atmosphere. Consequently, if this relative condition happens, the result
will be as I have stated.
Bodies may be colder than the atmosphere and yet derive no moisture from it;
while at the same time the driest atmosphere is not devoid of moisture, but willpart with it under certain conditions.
Assuming for granted that this relative condition between the plate andatmosphere, disposing the former to receive the humidity of the latter,
constitutes the great obstacle the operator has to contend with in producing, aclear proof upon the plate, the remedy naturally suggests itself, and is very
simple. It consists in merely heating the plate above the temperature of theatmosphere, previous to polishing, and retaining that temperature during theoperation. Various measures might be devised to effect the desired object; oneof which consists of a sheet-iron box, heated from the inside by a spirit-lamp,
upon the top of which are to be kept the plates ready to undergo the process of
being polished; the blocks of the swing or any other vice; or the iron bed
belonging to Lewis's vice.
In cold weather, when it is necessary to keep a fire in the preparation room,
all of the above may be so arranged in the vicinity of the fire as to receive
the requisite degree of heat for the purpose specified.
This part of the subject, however, is left entirely for the ingenuity of theoperator. No matter by hat means he accomplishes the object; all that isrequired is to heat the plate above the temperature of the atmosphere and retainthat heat during the process of polishing.
Since the adoption of this method. in connection with my partner, T. J. Dobyns,
even in this humid climate of ours, when everything in the room is dripping withmoisture, it has been attended with invariable success.

Choice Of Plates, Etc.
In the great catalogue of complaints made by operators, none is more common thanthat alleged against the quality of plates in general use. Although the greatest
diversity of opinion exists upon this subject, nevertheless the plates of every
manufactory share in this universal condemnation.
To be sure it cannot be denied but that this necessary article of utility in thephotographic art has undergone a sad deterioration in quality owing to theincreasing demand and great reduction in price--the plates of the present day
being by no means so heavily coated with silver as formerly--but the complaint
alluded to is not predicated so much upon the thinness of silver as upon amysterious something which has conferred upon the plates the epithet of not
good.
That this complaint is in a great measure groundless appears evident from thefact that while, with the same brand of plates one operator can work
successfully, another encounters the greatest difficulty; while one is able toproduce beautifully clear and altogether satisfactory results, the other labors
under the troublesome annoyance of innumerable specks, large dark insensitive
patches and brown map-like portions, together with divers other blemishes,sufficient to prevent him from obtaining anything like a tolerable impression.
From this wide difference in the results of the two operators using identicallythe same article, it is but reasonable to conclude that the complaint is foundedin error; while the inference is no more than just, that the fault may be traced
to a want of practical skill on the part of the complaining operator himself;
rather than to the inferior quality of the plates.
The question, then, whether the plates are unfit for use, or whether those who
pronounce them so understand how to use them, appears to be satisfactorily
answered. It therefore becomes a matter worthy of investigation, to ascertain
what superior judgment and skill one operator possesses over another whichenable him to work successfully a quality of plate, pronounced by the otherentirely useless.
Suppose we make a critical examination of one of the repudiated plates. From its
external appearance we have little hesitation in pronouncing it to be French;
indeed, this presumption is strongly corroborated by the fact that it isornamented upon one of its corners with a brand to designate the manufactoryfrom which it emanated.
Upon close inspection we cannot fail to notice a striking peculiarity upon thesurface; the roughness is very remarkable; the planishing hammer has left
amazingly visible indications of its busy work. One would suppose the
manufacturer intended the surface of the plate to represent the undulations of

the sea, instead of that smooth and level character so strongly recommended by
M. Daguerre.
Such a plate necessarily requires at the hand of the operator considerable labor
before the surface is in a proper condition to receive a suitable polish fromthe buffer. The least reflection in the world should teach any one that so longas the undulatory character continues upon the surface of the plate, it is in avery imperfect condition for buffing, because the buffer cannot touch every
point equally; the elevated portions alone receiving a high degree of polishwhile the depressed portion, from their roughness acting as nuclei, gather dust,
rouge, and other foreign bodies, so detrimental to sensitiveness. The secret ofthe superior judgment and skill of one operator over another, is intimately
connected with this point: his success depends very much upon the first processof cleaning the plate.
Let us examine the manipulation of the complaining operator. He takes one ofthese plates and gives it a careful scouring with rotten-stone and alcohol or
any other liquid preferred for this part of the operation--that is, he gives it
what he terms a careful scouring--very gently indeed because, from the frequent
trials he is in the habit of making in the camera, he fears he will rub thesilver entirely away before he succeeds in obtaining a good impression. The dark
patches, specks, and granular appearance resulting entirely from the unevennessof the surface of the plate, look like copper to him, and he is surprised thathe should have rubbed away the silver so soon, particularly by such delicate
handling.
The judgment and experience of the successful operator, however, teach him thatscouring injures a plate less than buffing. He knows that unless the hammer
marks be obliterated, he cannot by the buffer produce a surface of uniform
polish and sensitiveness, without which a fair proof is extremely doubtful; heknows that the time employed in the preliminary operation of cleaning the plate
properly is economy.
There is a style of French plates in the market, denominated heavy, which are
truly excellent, if properly managed. Much patience, however, is required toremove the marks of the hammer; but with tripoli and alcohol the surface isreadily cut down, and the plate is then susceptible of a beautiful black lustre
by polishing with the buffer. The complaining operator could not succeed by his
own method with one of the plates; he would encounter all manner of clouds andother unaccountable phenomena; he would imagine this plate entirely worn out
before it was half cleaned, and soon fix in his own estimation the reputation of
the heavy plate.
In making a choice of plates, therefore, it would appear to be a matter ofperfect indifference with an experienced operator what kind he would use, except
so far only as the labor required in cleaning them was to be taken into
consideration.

The distinction between a scale plate, a Scovill No. 1, S. F., heavy A, star,
crescent, eagle, or any other brand, consists in the superior finish of some,and the thinness of the silver in the cheaper qualities.
Consequently, let the complaining operator but employ the diligence inculcatedin this article, to clean his plate thoroughly, so as to bring it to a perfectly
even and level surface, and he will seldom be troubled with specks, clouds, dark
patches, and the host of other obstacles which heretofore have tormented him.

CHAPTER VI.
An account of Wolcott and Johnson's early experiments, in theDaguerreotype.
By JOHN JOHNSON. [From Humphrey's Journal, vol. ii 185l]
As a general thing, however perfect any invention may be deemed by the inventor
or discoverer, it falls to the lot of most, to be the subject of improvement andadvancement, and especially is this the case with those new projects in science
which open an untrodden field to the view of the artisan. Such has been, in aneminent degree, the case with the discovery first announced to the world by
Mons. Jean Jaques Claude Daguerre, of Paris, in the year 1839, and which excitedunbounded astonishment, curiosity and surprise. It may be questioned had anyother than Daguerre himself discovered a like beautiful combination, whether theworld would have been favored with details exhibiting so much care, patience andperseverance as the Daguerreotype on its introduction. Shortly after, thesedetails reached the United States, by Professor S. F. B. Morse, of New York, whowas, at the time of the discovery, residing in Paris. By this announcement, thewhole scientific corps was set in operation, many repeating the experiments,
following carefully the directions pointed out by Daguerre, as being necessary
to success. Among the number in the United States, was Alexander S. Wolcott(since deceased) and myself; both of this city. On the morning of the 6th day ofOctober, 1839, I took to A. Wolcott's residence, a full description ofDaguerre's discovery, he being at the time engaged in the department of
Mechanical Dentistry, on some work requiring his immediate attention, the work
being promised at 2 P.M. that day; having, therefore, no opportunity to read thedescription for himself (a thing he was accustomed to do at all times, wheninvestigating any subject). I read to him the paper, and proposed to him that if
he would plan a camera (a matter he was fully acquainted with, boththeoretically and practically), I would obtain the materials as specified byDaguerre. This being agreed to, I departed for the purpose, and on my return tohis shop, he handed me the sketch of a camera box, without at all explaining inwhat manner the lens was to be mounted. This I also undertook to procure. After2, P.M., he had more leisure, when he proceeded to complete the camera,
introducing for that purpose a reflector in the back of the box, and also toaffix a plate holder on the inside, with a slide to obtain the focus on theplate, prepared after the manner of Daguerre. While Mr. Wolcott was engaged withthe camera, I busied myself in polishing the silver plate, or rather silver
plated copper; but ere reaching the end preparatory to iodizing, I found I had
nearly or quite removed the silver surface from off the plate, and that being
the best piece of sliver-plated copper to be found, the first remedy at handthat suggested itself, was a burnisher, and a few strips were quickly burnishedand polished. Meantime. the camera being finished, Mr. Wolcott, after readingfor himself Daguerre's method of iodizing, prepared two plates, and placing themin the camera, guessed at the required time they should remain exposed to theaction of the light; after mercurializing each in turn, and removing the iodizedsurface with a solution of common salt two successful impressions were obtained,
each unlike the other! Considerable surprise was excited by this result, foreach plate was managed precisely like the other. On referring to Daguerre, no
explanation was found for this strange result; time, however, revealed to us
that one picture was positive, and the other negative. On this subject I shallhave much to say during the progress of the work. Investigating, the cause ofthis difference occupied the remainder of that day. However, another attempt wasagreed upon, and the instruments, plates, etc., prepared and taken up into an
attic room, in a position most favorable for light. Having duly arranged thecamera, I sat for five minutes, and the result was a profile miniature (aminiature in reality,) or a plate not quite three-eighths of an inch square.
Thus, with much deliberation and study, passed the first day in Daguerreotype-little dreaming or knowing into what a labyrinth such a beginning was hasteningus.
[Description of apparatus represented on pages 192 and 199:]
A.--The Box--about 4 inches long by about 2 outside diameter.
B.--The Reflector soldered to a brass screw, and mounted in therear of the box.
c.--The slide to regulate the focus to the plate holder.
d.--The standard to the plate holder screwed to the slide.
f.--The plate-holder frame having two small ledges, * *, for theplate to rest upon.
g.--The plate resting upon the ledge., * *, and kept against theframe by the spring h. The plates used were about 3/8 of an inchsquare.
A.--The window with the sashes removed.
B and C (p. 199) are large looking-glasses mounted as plain reflectors, thelower one C having rotary motion upon the saddle, resting upon the sill of thewindow in order to direct the rays of the sun upon the reflector B, at any hourof the day--the vertical motion of the reflector Cbeing necessary, the sun varying in altitude so much during the hours mostfavorable to the production of portraits. The reflector C waskept up to the required position by the handle lever, upright post and bolts.
Reflector B was hinged at its upper end at the top of the window frame, the only
motion being necessary was that which would reflect upon the sitter the incident
rays from reflector C--the reflector B being kept at the required angle by theconnecting lever m, etc. Suitable back-grounds were placed behind the sitter.
The reflector B and C, had frequently to be renewed, the heat of the sun soon
destroying their brilliance or power of reflecting, light, before renewing them,
however, we resorted to the springing of them, by which means their power wasincreased for a period.
The camera or reflecting apparatus, invented by Mr. Wolcott, was, from thenature of the case, better adapted at that day to the taking of portraits fromlife, than any other instruments. After carefully examining the camera describedby Daguerre, and the time stated as necessary to produce action for an image, it
became evident to the mind of Mr. Wolcott at once, that more light could beobtained (as the field of view required was not large) by employing a reflectorof short focus and wide aperture, than from a lens arrangement, owing tospherical aberration and other causes. Many experiments having been tried withthe small instrument figured (p. 199), a reflector for taking portraits fromlife was determined on, having eight inches diameter, with twelve inches focal
distance for parallel rays; this was to admit plates of two inches wide by two
and a half long Mr. Wolcott having on hand reflectors of the right diameter, for
Newtonian telescopes, of eight feet focal distance, resolved (as it was a matterof experiment) to grind down or increase the curve for the focal distance before
named--this required time. In the mean time, many plans were pursued for making
good plates, and the means of finishing, them. As the completion of the large
reflector drew to a close, our mutual friend, Henry Fitz, Jr., returned fromEngland, whither he had been on a visit, and when he heard what we were about,kindly offered his assistance; he being well versed in optics, and having been
before engaged with Mr. Wolcott, in that and other business is offer was gladly
accepted--Mr. Wolcott himself having frequent engagement; to fill as operator in
the details of mechanical dentistry. Thus, by the aid of Mr. Fitz, the reflector
was polished, and experiments soon after tried on plates of two by tow and ahalf inches, with tolerable success. Illness on my part quite suspended further
trial for nearly four weeks.
On my recovery, early in January, 1840, our experiments were again resumed withimproved results, so much so as to induce Mr. Wolcott and myself to entertain
serious thoughts of making a business of the taking of likenesses from life,
intending to use the reflecting apparatus invented by Mr. Wolcott, and for which
he obtained Letters Patent, on the 8th day of May, 1840. Up to January 1st,
1840, all experiments had been tried on an economical scale, and the apparatus
then made, was unfit for public exhibition; we resolved to make the instruments
as perfect as possible while they were in progress of manufacture. Experiments
were made upon mediums for protecting the eyes from the direct light of the sun,and also upon the best form and material for a back-ground to the likenesses.
The length of time required for a "sitting," even with the reflecting apparatus,
was such as to render the operation anything but pleasant. Expedients were everready in the hands of Wolcott: blue glass was tried and abandoned in consequenceof being, at that time, unable to procure a piece of uniform density andsurface: afterwards a series of thin muslin screens secured to wire frames wereprepared as a substitute for blue glass. The objections to these screens,however, were serious, inasmuch as a multiplication of them became necessary tolessen the intensity of the light sufficiently for due protection to the eyes,
without which, the likenesses, other than profiles, were very unpleasant to lookupon. Most of the portraits, then of necessity were profiles formed upon backgrounds, the lighter parts relieved upon black, and the darker parts upon light
ground; the back-ground proper being of light colored material with black velvet
so disposed upon the light ground, this being placed sufficiently far from thesitter, to produce harmony of effect when viewed in the field of the camera.
Other difficulties presented themselves seriously to the working of the
discovery of Daguerre, to portrait taking--one of which was the necessity for aconstant and nearly horizontal light, that the shaded portions of the portrait
should not be too hard, and yet, at the same time, be sufficiently welldeveloped without the "high light" of the picture becoming overdone, solarized
or destroyed. In almost all the early specimens of the Daguerreotype, extremesof light and shade presented themselves, much to the annoyance of the early
operators, and seriously objectionable were such portraits. To overcome thisdifficulty, Mr. Wolcott mounted, with suitable joints, upon the top of his
camera, a large looking-glass or plane reflector, in such a manner that thelight of the sun (as a strong light was absolutely necessary), when falling upon
the glass could be directed upon the person in an almost horizontal direction.
Early in February, 1840, Mr. Johnson, Sen., (since deceased) sailed for Europe
with a few specimen likenesses taken with the instruments completed as above,with the intention of patenting the invention. On his arrival a joint
arrangement was effected with Mr. Richard Beard, of London, in patenting andworking the invention in England. Up to February, 1840, but few friends had been
made acquainted with the progress of the art in the hands of Mr. Wolcott andmyself. From time to time reports reached us from various sources of the successof others, and specimens of landscapes, etc., were exhibited at Dr. James R.
Chilton's laboratory, in Broadway, much to the gratification of the numerous
visitors and anxious expectants for this most wonderful discovery. Dr. Chilton,
Professor J. J. Mapes, Professor J. W. Draper. Professor S. F. B. Morse, all of
this city; Mr. Cornelius, Dr. Goddard and others of Philadelphia; Mr.
Southworth, Professor Plumbe, and numerous others were early in the field; all,however, using the same description of camera as that of Daguerre, withmodification for light, either by enlargement by lens and aperture for light, orby shortening the focal distance.
At a conversational meeting of the Mechanics' Institute, Professor J. J. Mapes
being present, a question was asked if any one present could give information
relative to portraiture from life by the Daguerreotype. Mr. Kells, a friend of

Mr. Wolcott and a scientific and practical man (sinced deceased), at once marked
out upon the black-board, the whole as contrived by Mr. Wolcott. This gave
publicity to the invention of Mr. Wolcott. Shortly after, Professor Mapes, Dr.
Chilton, and many others, sat for their portraits, and were highly gratified.
Professor Morse also came and proposed to Mr. Wolcott to join him in the workingof the invention, etc.
From this time much interest was manifested by our friends in our progress.
Rooms were obtained in the Granite Buildings, corner of Broadway and Chambers
street, and fitted for business. The rooms being small, it was soon foundimpracticable to use the arrangement of looking-glass, as previously spoken of;a new plan became necessary, to introduce which, the sashes were removed,

and two large looking-glasses were mounted in proper frames, thus:--Just in front, and between the sitter and[page 200]
the reflector, upon a proper stand, were used those paper muslin screen before
described; also screens of tissue paper. These screens. however, when they wereused, required so much time for a sitting, that some other medium, as aprotection to the eyes, became absolutely necessary. The most plausible thingthat suggested itself was blue glass; but, as this could not be found, numerous
were the expedients proposed by the friends of the art, who from time to time
visited our rooms. At the suggestion of Professor Mapes (who is ever ready toassist those in perplexity), a trough of plate glass s, about twenty-eight
inches square in the clear, and from three to four inches thick, was filled witha solution of ammonia sulphate of copper, and mounted on the frame as in thesketch, which, for a time, answered extremely well; soon, however, decompositionof this solution became apparent from the increased length of time required fora sitting, although to the eye of an observer, no visible cause for such long
sittings could be pointed out. Professor Mapes being appealed to, suggested thatto the above solution a little acid be added which acted like a charm-shortening the time for a sitting from six, eight, or ten minutes to that ofabout one. Decomposition, however, would go on by the action of light and heatthrough the solution. New solutions were tried, when the whole were finallyabandoned as being, too uncertain and troublesome. (The reflecting apparatus R,
was placed upon the stand as in the sketch, with a wedge for elevating thecamera, between it and the table, to obtain the image properly upon the plate.)
A quantity of blue window glass was next obtained, and holes drilled through thecorners of it, and several sheets were wired together to increase the size, and,
when complete, was suspended from the ceiling in its proper place, and so
arranged that when a person was sitting, this sheet of glass could be moved toand from, the object of which was to prevent shadows on the face of the sitter
produced from the uneven surface of the glass. This latter contrivance was useduntil a perfect plate of glass was procured.
The number of persons desirous of obtaining, their miniatures, induced many toentertain the idea of establishing themselves in the Art as a profession, andnumerous were the applications for information; many persons paying for theirportraits solely with the view of seeing the manner of our manipulations, inorder that they might obtain information to carry on likeness-taking as abusiness.
The reflecting camera being a very troublesome instrument to make, anddifficulties besetting us from every source, but little attention could be given
to teaching others; and, indeed, as the facts seemed to be at this time, we knew
but little of the necessary manipulations ourselves. In course of time, several
established themselves. The first one, after ourselves, who worked the discovery
of Daguerre for portrait taking in this city, was a Mr. Prosch; followed soonafter by many others, in almost all cases copying the reflecting arrangement forlight, as figured above, many using it even after we had long abandoned that
arrangement for a better one.
Innumerable obstacles to the rapid advance of the daguerreotype, presented
themselves almost hourly, much to the annoyance of ourselves, and thosedependent upon our movements for their advancement. Among the most difficult
problems of the day, was the procuring of good plates. Messrs. Corduran & Co.
were among the first to supply the trade; at that early day, however, it was avery rare thing, to be able to procure an even perfect surface, from the fact

that a pure surface of silver could scarcely be obtained, the manufacturers
deeming it too much trouble to prepare silver plated copper with pure silver-the result was, that in attempting to polish perfectly such plated metal as
could be procured, the plates would become cloudy, or colored in spots, from thefact of having more or less alloy, according as more or less of the silver
surface was removed in polishing the plate fit for an impression. To explain
more clearly, it was the practice of most silver platers to use an alloy forsilver-plating. In the reduction of the ingot to sheet metal, annealing has tobe resorted to, and acid pickles to remove oxides, etc. The number of times theplated metal is exposed to heat and acid in its reduction to the required
thickness, produces a surface of pure silver. The most of this surface is,however, so rough as to be with difficulty polished, without in places removing
entirely this pellicle of pure metal, and exposing a polished surface of thealloy used in plating. Whenever such metal was used, very unsightly stains or
spots frequently disfigured the portraits. The portrait, or portion of it,
developed upon the pure silver, being much lighter or whiter than that developed
upon the alloy; it therefore appeared that the purer the silver, the moresensitive the plate became. Accordingly, we directed Messrs. Scovills, ofConnecticut, to prepare a roll of silver-plated metal, with pure silver; it
fortunately proved to be a good article, but, unfortunately, a pound of thismetal (early in 1840) cost the round sum of $9. Like descriptions of metal, thesame gentlemen would be glad to furnish, at this time, for $4. Soon after this,some samples of English plated metal, of a very superior quality, came to ourpossession, and relieved us from the toil of making and plating one plate at atime, an expedient we were compelled to resort to, to command material to meetthe pressing demands for portraits.
Having it now in our power to obtain good plated metal, a more rapid mode ofpolishing than that recommended by Daguerre was attempted as follows:This metal was cut to the desired size, and having a pair of "hand rolls" athand, each plate, with its silvered side placed next to the highly polishedsurface of a steel die, was passed and repassed through the rolls many times, bywhich process a very smooth, perfect surface was obtained. The plates were thenannealed, and a number of plates thus prepared were fastened to the bottom of abox a few inches deep a foot wide, and eighteen inches long; this box was placed
upon a table and attached to a rod connected to the face plate of a lathe, a few
inches from its centre, so as to give the box a reciprocating motion. A quantityof emery was now strewn over the plates, and the lathe set in motion. The action
produced wag a friction or rubbing of the emery over the surface of the plates.
When continued for some time, a greyish polish was the result. Linseed, whenused in the same manner, gave us better hope of success, and the next step
resorted to was to build a wheel and suspend it after the manner of agrindstone. The plates being secured to the inner side of the wheel or case, andas this case revolved, the seeds would constantly keep to the lower level, andtheir sliding over the surface of the plates would polish or burnish theirsurfaces. This, with the former, was soon abandoned; rounded shots of silver

placed in the same wheel were found not to perform the polishing so well as
linseed. Buff-wheels of leather with rotten-stone and oil, proved to be far
superior to all other contrivances; and, subsequently, at the suggestion ofProfessor Draper, velvet was used in lieu of buff leather, and soon superseded
all other substances, both for lathe and hand-buffs, and I would add, for the
benefit of new beginners that those who are familiar with its use, prefer cotton
velvet. The only requisite necessary is, that the buffs made of cotton velvet
should be kept dry and warm.
The greater number of operators, with whose practice I am familiar, use, forpolishing plates, prepared tripoli, imported from France, or Browne's rottenstone. The former of these articles is very objectionable, inasmuch as there isno positive certainty of being enabled to procure or make the article of uniform
grit--the nature of the substance rendering, it impossible to reduce it tovarying degrees of evenness, by the well known process of washing, for that
purpose, and the burning of rotten-stone changes its chemical nature somewhat,at the same time rendering, this invaluable article harsh and gritty. And
especially, no reliance can be placed upon burned rotten stone if purchased fromthose who do not give very great attention and care to its preparation; and thesame remarks apply to rouge.
The best article for polishing Daguerreotype plates is rotten-stone, such as canbe procured in any town, prepared after the following manner: Procure, say halfa dozen wide-mouthed bottles, of suitable dimensions, numbering each from one tosix. Put into No. 1 about half a pound of rotten-stone. and nearly fill thebottle with water. Then, with a proper stick or spatule, mix well the rottenstone and water; after which, let No. 1 rest for, say one minute, then carefully
pour off into bottle No. 2 (or, what would be better, draw off by a syphon) as
much of the floating particles of rotten-stone as is suspended in the water.
Again fill bottle No. 1 with water, agitate it as before, and decant it tobottle No. 2, care being taken to draw off only the suspended particles ofrotten-stone.
When a sufficient quantity of washings from bottle No. 1 is collected into
bottle No. 2, a similar process must be gone through. as above stated, for No.
1; the difference being in the care required, and in the time allowed between
the stirring or mixing the rotten-stone and water. The floating particles ofrotten-stone, after four minutes' subsiding, will be found fine enough for thefinest Daguerreotype polishing required.
A quantity of such washings may be collected in a large bottle, and allowed tostand a few hours, when all the rotten-stone will have settled. The water may be
poured off and the rotten-stone put into an evaporating dish, and while being
dried, must be constantly stirred to obtain an impalpable powder.
Further washings may in like manner be resorted to for finer qualities ofrotten-stone. In my practice, I have used the articles at two and four minutes'
settling, and occasionally have prepared it after standing for eight minutes. Sofine a quality as this, however, is seldom required. In using, rotten-stone, I
mix with it, for polishing, fine olive oil, until I obtain a thin paste--and thebest of all methods for polishing (well planished) Daguerreotype plates, is one
like that used for glass by lens polishers; that is, by using a disc or buffwheel, and having, a suitable holder by which to secure the plate, and then bypressing the plate against the revolving buff, well saturated with the mixed oiland rotten-stone, a very good surface is obtained. A quantity of plates may be
prepared in this way, and all the adhering oil, etc., may be removed by a clean
hand, or lathe buff, after which each plate must be heated to the point
necessary to burn off the remaining oil great care being required not tooverheat the plate. A very slight excess of temperature will at once destroy all
the polish previously obtained. The test for ascertaining the right temperature
is at hand; the adhering oil will be driven from the plate in the form of smoke
when the right temperature is reached. The moment the smoke ceases to rise fromthe plate, the heat must he removed, and the plate quickly cooled upon a pieceof iron.
A quantity of plates thus prepared may be kept on hand for any required time,
and the labor of one minute, with a lathe or hand-buff with dry charcoal, or
rather, prepared lampblack, will perfectly polish the surface ready forindexing, etc. This lampblack also requires some care in preparing. Take asmall-size crucible, properly temper it by a slow fire, that it may not be
cracked after which, fill it with common lampblack, cover it over with a pieceof soap-stone, and again replace it in the fire. Build a good hard coal firearound it continue the heat for two or three hours, being careful not to raise
the cover till the crucible be quite cold. Pulverize when using it. It is very
desirable to keep this lampblack dry and warm. Some operators use much rouge I
would recommend the above in preference; but those who feel that they cannot
dispense with the use of rouge, had better try a large addition of preparedlampblack to a small one of rouge, as this latter article, unless great pains betaken in its preparation, will adhere and work itself into the body of thesurface, so that it cannot be removed therefrom; and I have seen many specimensof Daguerreotype very much injured in effect from this rouge tint disseminatedthroughout their shaded features, at the same time that the whole general effectof such pictures is that of a want of life. It is true that with the use ofrouge a very high degree of polish may be obtained, but probably not higher thancan be produced with many other substances of a less objectionable nature.
From the announcement of the discovery by Daguerre to the beginning of the year
1840, I am not aware of any attempt to lessen the time for the action of animage, or an impression, other than that of the reflecting camera invented by
Mr. Wolcott. Early, however, in 1840, Mr. Wolcott was desirous to be enabled tofurther shorten the time for a sitting, and having some knowledge of bromine andits action, by request, Dr. Chilton prepared a small quantity; but Mr. Wolcott
did not succeed very well with it, he having invariably used too much incombination with iodine to produce that sensitive coating now well known to theprofession. Professor Morse, of this city, Dr. Goddard, of Philadelphia, andothers, in the years 1840 and 1841, were acquainted with the use of bromine. N.

Griffing, of this city, or myself, used with tolerable success, iodine in large
excess to nitric acid and water; and, subsequently, to nitro muriatic acid(which reacted and formed a peculiar chloride of iodine); this latter
combination proved to be preferable to simple iodine, at the same time somewhat
more sensitive, and was used by me in this city up to the time of my leaving for
London (October 1, 1840). On arriving in London, I instituted a series ofexperiments in the various chemical combinations, solely with the view to beenabled to obtain more speedily a portrait than it was practicable to do withany known chemicals at that date. The high latitude, and the winter season of
the year rendering but a feeble light at best, the greater the necessity for amore sensitive chemical preparation to the shortening the time for a sitting.
Near the beginning of the year 1841, I discovered and practically applied,
chloride of iodine to great advantage, and, as far as memory serves me, I
believe the first used in this country was some made and shipped, Messrs.
Harnden & Co., from London, to Mr. Wolcott, in New York.
About the same time, Mr. John Goddard, of London (who was associated withmyself), discovered a rather valuable combination of chemicals, consisting of a
mixture of iodine, bromine, iodus, and iodic acid, and a proper combination of
those bodies gave an action somewhat more sensitive than chloride of iodine--butthe "high lights" of the portraits would become solarized or overdone, more
frequently with this combination than with the chloride of iodine. Throughout
the year 1841, I used, with great success, chloride of iodine, applied as one
coating--occasionally in conjunction with Mr. Wolcott, attempting the use ofiodine, bromine, and chlorine, and at times with more or less success. The
difficulty of exactly combining, the three elements above mentioned, in order toproduce a certainty of result with harmony of effect, was the work of many
months, with great labor and study, the slightest modification requiring a long,series of practical experiments, a single change consuming, frequently, anentire day in instituting comparisons, etc., etc.
Early in the year, 1842, I discovered a combination of chemicals (now known in
London as "Wolcott's Mixture," in hermetically sealed bulbs) of exceeding
uniform character, very sensitive to the action of light, and specimens producedin 1842-3, with this combination, will bear comparison with the best specimens
produced at this late date.
About the same time, I discovered that however much overdone a Daguerreotype
might be, the means were at hand to save or redeem it. It has long, since been
known to operators, that if a plate be exposed to light after being coated,
unless it be again coated, a clear and distinct picture could not be obtained
upon the same plate without first repolishing and recoating the same, care being
taken that no light fall upon the prepared surface. To prevent solarization,coat a plate as usual, expose to the action of light any required time(according to circumstances), say from quarter to one half more time than would
be required in the ordinary method of procedure; observe, before putting theplate in the mercury box, place it over the vapor of iodine, bromine, or
chlorine, etc. (carefully excluding the light), for a very brief period, greatcare being required to have the selected vapor very much diluted with air, inorder to success. Many experiments will be required ere arriving at satisfactory
results. Specimens now unknown to general operators, for harmony of effect, havebeen, and may again be produced by the method pointed out above. I have foundthe best general effect, and the most certain result to follow from the use of
the vapor of chlorine--but this requires more than ordinary care. I would,
therefore, recommend the use of iodine. Thus: to a few grains of iodine, add anounce of warm water (which will become tinged with iodine); when cold, to half apint of pure water in a new and clean coating box, put, of the above, fifty
drops; stir and mix well this small quantity of iodine in with the water; in ten
minutes this box will be ready for use. Great care and judgment will be requiredin the application of this vapor to the plate; if the plate remain over thevapor too long. the developed picture will have a faint and misty appearance; if
not exposed long enough, the "high light" will be solarized. I have great hopeof the ultimate use of this process, as it is the only means yet discovered to
be enabled to secure specimens of extremes of light and shade, yet producing
harmony of effect; and I would call the attention of the profession to the fact,that a plate may be exposed to the action of light for any length of time (athousand times longer than required to act for the lesser quantity of mercury todeposit itself, or that amount necessary to form a perfect specimen), and berestored by the application of any of the vapors above mentioned, remarking thatfor extremes for solarization, denser vapors will be required. Much remains to
be done with this discovery to the application of the Daguerreotype.