IMPROVEMENTS IN THE ART OF ENGRAVING
Year: 1858

page_text: LETTERS PATENT to William Henry Fox Talbot, of Lacock Abbey, in
the County of Wilts, Esquire, for the Invention of "IMPROVEMENTS IN
THE ART OF ENGRAVING."
Sealed the 15th June 1558, and dated the 21st April 1858.
PROVISIONAL SPECIFICATION left by the said William Henry Fox
Talbot at the Office of the Commissioners of Patents, with his Petition,
on the 21st April 1858.
I, WILLIAM HENRY FOX TALBOT, of Lacock Abbey, in the County of Wilts,
Esquire, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN THE ART OF ENGRAVING," to be as follows
I take a very clean metal plate, either of copper, zinc, or steel, as prepared
for the use of engravers, and I pour upon it a mixture of gelatine with
bichromate of potash. When this film is dry I place upon it the object to
be copied, which may either be an actual substance, as the leaf of a plant, a
piece of lace, &c., or it may be an engraving, or a printed page, or else it
may be a photograph representing any object. This is to be placed in a
copying frame, and screwed into close contact with a film of gelatine on
the metal plate, then placed in daylight or sunshine till a photographic
impression is effected on the gelatine. So far the process is identical with

page_text: that described by me in the Specification of my Patent for improvements in
the art of engraving, bearing date the 29th day of October, in the year 1852.
The novelty of the present Invention is in the mode of etching the image or
picture obtained in the manner before mentioned,and which is done as follows:
-I do not wash the picture or image, which I find not to be necessary, but
as soon as it is removed from the copying frame I cover or sprinkle the whole
of its surface with very fine powder of copal or other resin. Then I melt this
powder by heating it over a lamp. When the plate has grown cold I pour
upon it a solution of perchloride of iron in water nearly saturated, and yet
not quite saturated, which soon effects an etching if the process is well con-
ducted. Sometimes I use other metallic chlorides and other salts with an
acid reaction capable of etching the metallic plates. When the etching is
effected the etching liquid is washed off with a rapid current of cold water; the
plate is then cleaned with warm water, whiting, &c. Although as I have said
it is not necessary to wash the photographic image when first taken out of the
copying frame, nevertheless that process may be adopted, if preferred. In
that case it is best to wash the image on the metal plate with a mixture of
water and spirits of wine in equal portions, then to wash it with spirits of
wine alone, then to dry it, then to dip the metal plate into warm water for
half a minute, and then to dry it again thoroughly, after which the powdered
resin is to be put on, and the rest of the process conducted as it is above
described, except that the etching liquid ought to be more diluted with
water. I also employ the perchloride of iron for the purpose of ordinary
etching, in lieu of aquafortis or nitric acid, which is commonly employed by
engravers.
Another part of my Invention is as follows:-I take a plate of copper,
zinc, or steel, and engrave or etch it all over, so that it will print a dark
and uniform shade upon paper; I then cover it with a mixture of gelatinė
and bichromate of potash, and make a photographic image upon it, as
above described; I then wash the picture in the manner above described,
by which the parts of the metal plate on which light has not acted are
denuded of the gelatine, or partly so, exposing when the plate is dry the
etched surface of the metal, while the parts on which light has acted
strongly remain smooth, being covered with a thick coating of gelatine; Ithen
take a slab of rather warm gutta percha and press it on the metal plate in a
press; it will take the impression of the design cr picture on the metal plate;
I then electrotype the gutta percha, having first made its surface conductive of
electricity, and thus I obtain an electrotyped etching; and to the processes
herein described I have given the name of photoglyphic engraving. By a nearly

page_text: similar process a photographic etching may be made upon the surface of the
stones usually employed for lithography.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Henry Fox Talbot in the Great Seal Patent Office
on the 14th October 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, 1, WILLIAM
HENRY FOX TALBOT, of Lacock Abbey, in the County of Wilts, Esquire, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by.Her Letters
Patent, bearing date the Twenty-first day of April, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Henry Fox Talbot, Her special licence that I, the said William
Henry Fox Talbot, my executors, administrators, and assigns, or such others
as I, the said William Henry Fox Talbot, my executors, administrators, and
assigns, should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE ART OF ENGRAVING," upon the condition (amongst
others) that I, the said William Henry Fox Talbot, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the said
Invention, and in what manuer the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Henry Fox Talbot, do hereby
declare the nature of the said Invention, and in what mauner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:—
The process described in this Specification, to which I have given the name
of photoglyphic engraving, is performed in the following manner :-In this
Invention I employ plates of steel, copper, or zinc, such as are commonly used
by engravers. Before using a plate, its surface should be well cleaned. It
should then be rubbed with a linen cloth dipped in a mixture of caustic soda
and whiting, in order to remove any remaining trace of greasiness. The plate

page_text: is then to be rubbed dry with another linen cloth; this process is then to be
repeated, after which the plate is in general sufficiently clean.
In order to
engrave a plate, I first cover it with a substance which is sensitive to light.
This is prepared as follows:-About a quarter of an ounce of gelatine is dis-
solved in 8 or 10 ounces of water by the aid of heat. To this solution is added
about one ounce by measure of a saturated solution of bichromate of potash in
water, and the mixture is strained through a linen cloth. The best sort of
gelatine for the purpose is that used by cooks and confectioners, and commonly
sold under the name of gelatine. In default of this, isinglass may be used, but
it does not answer so well. Some specimens of isinglass have an acidity which
slightly corrodes and injures the metal plates. If this accident occurs,
ammonia should be added to the mixture, which will be found to correct it.
This mixture of gelatine and bichromate of potash keeps good for several
months, owing to the antiseptic and preserving power of the bichromate. It
remains liquid and ready for use at any time during the summer months, but
in cold weather it becomes a jelly, and has to be warmed before using it. It
should be kept in a cupboard or dark place. The proportions given above are
convenient, but they may be considerably varied without injuring the result:
The engraving process should be carried on in a partially darkened room, and
is performed as follows: A little of this prepared gelatine is poured on the
plate to be engraved, which is then held vertical and the superfluous liquid
allowed to drain off at one of the corners of the plate; it is then held in a
horizontal position over a spirit lamp which soon dries the gelatine, which is
left as a thin film of a pale yellow colour, covering the metallic surface and
generally bordered with several narrow bands of prismatic colours. These
colors are of use to the operator by enabling him to judge of the thinness of
the film. When it is very thin, the prismatic colours are seen over the whole
surface of the plate, such plates often make excellent engravings, nevertheless,
it is perhaps safer to use gelatine films which are a little thicker. Experience
alone can guide the operator to the best result. The object to be engraved is
then laid on the metal plate and screwed down uponit in a photographic copying
frame; such objects may be either material substances, as lace, the leaves
of plants, &c., or they may be engravings, or writings, or photographs, &c., &c.
The plate bearing the object upon it is then to be placed in the sunshine for a
space of time varying from one to several minutes, according to circumstances,
or else it may be placed in common daylight, but of course for a longer
time. As in other photographic processes, the judgment of the operator is
here called into play, and his experience guides him as to the proper time of
exposure to the light. When the frame is withdrawn from the light and the

page_text: object removed from the plats, a faint image is seen upon it, the yellow colour
of the gelatine having turned brown wherever the light has acted. This process
so far as I have yet described it, is in all essential respects identical with that
which I have described in the Specification of my former Patent for improve-
ments in engraving, bea ing date the 29th October 1852.
The novelty of the present Invention consists in the improved method by
which the photographic image obtained in the manner above described is
engraved upon the metal plate.
The first of these improvements is as follows:-I formerly supposed that it
was necessary to wash the plate bearing the photographic image in water, or
in a mixture of water and alcohol, which dissolves only those portions of the
gelatine on which the light has not acted. And I believe that all other persons
who have employed this method of engraving by means of gelatine and bichro-
mate of potash have followed the same method; viz., that of washing the
photographic image. But however carefully this process is conducted, it is
frequently found when the plate is again dry, that a slight disturbance of the
image has occurred, which of course is injurious to the beauty of the result.
And I have now ascertained that it is not at all necessary to wash the photo-
graphicimage. On the contrary, much more beautiful engravings are obtained
upon plates which have not been washed, because the more delicate lines and
details of the picture have not been at all disturbed.
The process which I
now employ is as follows: When the plate bearing the photographic image is
removed from the copying frame, I spread over its surface, carefully and very
evenly, a little finely powdered gum copal (in default of which common resin
may be employed). It is much easier to spread this resinous powder evenly
upon the surface of the gelatine than it is to do so upon the naked surface of
a metal plate. The chief error the operator has to guard against is that of
putting on too much of the powder; the best results are obtained by using a
very thin layer of it, provided it is uniformly distributed. If too much of the
powder is laid on, it impedes the action of the etching liquid. When the
plate has been thus very thinly powdered with copal, it is held horizontally
over a spirit lamp, in order to melt the copal; this requires a considerable
heat. It might be supposed that this heating of the plate, after the formation
of a delicate photographic image upon it would disturband injure that image,
but it has no such effect; the melting of the copal is known by its change of
color; the plate should then be withdrawn from the lamp and suffered to cool.
This process may be called the laying an aquatint ground upon the gelatine,
and I believe it to be a new process.
In the common mode of laying an aquatiut ground, the resinous particles

page_text: are laid upon the naked surface of the metal, before the engraving is com-
menced. The gelatine being thus covered with a layer of copal disseminated
uniformly and in minute particles, the etching liquid is to be poured on; this
is prepared as follows:-Muriatic acid, otherwise called hydrochloric acid, is
saturated with peroxide of iron, as much as it will dissolve with the aid of
heat; after straining the solution to remove impurities, it is evaporated tillit
is considerably reduced in volume, and is then poured off into bottles of a
convenient capacity; as it cools it solidifies into a brown semi-crystalline
mass; the bottles are then well corked up and kept for use.
I shall call this preparation of iron by the name of perchloride of iron in
the present Specification, as I believe it to be identical with the substance
described by chemical authors under that name. For example, see Turner's
Chemistry, 5th editi n,page 537,and by others called permuriate of iron. För
example, see Brande's Manual of Chemistry, 2nd edition, vol. 2, page 117; it
is a substance very attractive of moisture. When a little of it is taken from a
bottle in the form of dry powder and laid upon a plate, it quickly deliquesces,
absorbing the atmospheric moisture; in solution in water it forms a yellow
liquid in small thicknesses, but chesnut brown in greater thicknesses. In
order to render its mode of action in photoglyphic engraving more intelligible,
I will first state that it can be very usefully employed in common etching,
that is to say, that if a plate of copper, steel, or zinc is covered with an
etching ground, and lines are traced on it with a needle's point so as to form
any artistic subject, then if the solution of perchloride of iron is poured on,
it quickly effects an etching, and does this without disengaging bubbles of gas
or causing any smell, for which reason it is much more convenient to use
than aquafortis, and also because it does not injure the operator's hands or
his clothes if spilt upon them. It may be employed of various strengths for
commonetching, butrequires peculiarmanagement forphotoglyphic engraving,
and as the success of that mode of engraving chiefly turns upon this point, it
should be well attended to.
Water dissolves an extraordinary quantity of perchloride of iron, sometimes
evolving much heat during the solution. I find that the following is a con-
venientwayof proceeding: A bottle (No.1) is filled with a saturated solution
of perchloride of iron in water; a bottle (No.2), with a mixture consisting of 5
or 6 parts of the saturated solution and 1 part of water; and a bottle (No 3),
with a weaker liquid consisting of equal parts of water and of the saturated
solution. Before attemptingan engraving of importance, it is almost essential to
make preliminary trials in order to ascertain that these liquids are of the proper
strengths. These trials I shall therefore now proceed to point out. I have already

page_text: explained how the photographic image is made on the surface of the gelatine,
and covered with a thin layer of powdered copal or resin, which is then melted
by holding the plate over a lamp; when the plate has become perfectly cold, it'
is ready for the etching process, which is performed as follows:-A small
quantity of the solution in bottle, No. 2, namely, that consisting of 5 or 6
parts saturated solution to 1 of water is poured upon the plate, and spread
with a camel hair brush evenlyall over it. It is not necessary to make a wall
of wax round the plate, because the quantity of liquid employed is so small,
that it has no tendency to run off the plate. The liquid penetrates the gelatine
wherever the light has not acted on it, but it refuses to penetrate those parts
upon which the light has sufficiently acted.
It is upon this remarkable fact that the art of photoglyphic engraving is
mainly founded. In about a minute the etching is seen to begin, which is
known by the parts etched turning dark brown or black, and then it spreads
over the whole plate, the details of the picture appearing with great rapidity
in every quarter of it. It is not desirable that this rapidity should be too
great, for in that case it is necessary to stop the process before the etching
has acquired sufficient depth (which requires aa action of some minutes'
duration). If, therefore, the etching on trial is found to proceed too rapidly,
the strength of the liquid in bottle No. 2 must be altered (by adding some of
the saturated solution to it), before it is employed for another engraving. But
if, on the contrary, the etching fails to occur after the lapse of some minutes,
or if it begins, but proceeds too slowly, this is a sign that the liquid in
bottle No. 2 is too strong, and too nearly approaching saturation. To correct
this a little water must be added to it before it is employed for another
engraving; but in doing this the operator must take notice that a very minute
quantity of water added often makes a great difference, and causes the liquid
to etch very rapidly; he will therefore be careful in adding water not to
do so too freely. When the proper strength of the solution in bottle No. 2
has thus been adjusted, which generally requires 3 or 4 experimental trials, it
can be employe.l with security. Supposing, then, that it has been ascertained:
to be of the right strength, the etching is commenced as above mentioned, and
proceeds till all the details of the picture have become visible, and present a
satisfactory appearance to the eye of the operator, which generally occurs in
two or three minutes, the operator stirring the liquid all the time with a camel
hair brush, and thus slightly rubbing the surface of the gelatine, which has a
good effect. When it seems likely that the etching will improve no farther, it
must be stopped; this is done by wiping off the liquid with cotton wool, and
then rapidly pouring a stream of cold water over the plate, which carries off

page_text: all the remainder of it. The plate is then wiped with a clean linen cloth, and
then rubbed with soft whiting and water to remove the gelatine. The etching
is then found to be completed.
I will now describe another etching process very slightly differing from the
former, which I often use:-When the plate is ready for etching, pour upon
it a small quantity of the liquid (No. 1) (the saturated solution); this should be
allowed to rest upon the plate 1 or 2 minutes; it has no very apparent effect,
but it acts usefully in hardening the gelatine. It is theu poured off from the
plate, and a sufficient quantity of solution No. 2 is poured on. This effects
the etching in the manner before described. And if this appears to be quite
satisfactory, nothing further is required to be done. But it often happens that
certain faint portions of the engraving, such as distans mountains or buildings
in a landscape, refuse to appear, and as the engraving would be imperfect
without them, I recommend the operator in that case to take some of the weak
liquid No. 3 in a little saucer, and without pouring off the liquid No. 2 which
is etching the picture, to touch with a camel hair brush dipped in liquid No. 3
those points of the picture where he wishes for an increased effect. This
simple process often causes the wished for details to appear, and that some-
times with great rapidity, so that caution is required in the operator in using
this weak solution No. 3, especially lest the etching liquid should penetrate to
the parts which ought to remain white. But in skilful hands its employment
cannot fail to be advantageous, for it brings out soft and faint shadings, which
improve the engraving, and which would otherwise probably be lost. Ex.
perience is requisite in this as in most other delicate operations connected with
photography; but I have endeavoured clearly to explain the leading principles
of this new process of engraving according to the mode which I have hitherto
found the most successful.
With respect to the second Invention mentioned in my Provisional Specifi-
cation, in which the electrotype process is employed, I have found that it gives
less successful results than that which I have fully described above, and I have
therefore omitted it from this Specification, and make no claim with respect
to it. In conclusion, I would remark that besides the process of photoglyphic
engraving considered as a whole being new, I believe the following points also
to be new, viz*.:-
First, the etching a photographic image formed upon a surface of gelatine
and bichromate of potash without first disturbing that surface by washing it
with water or alcohol.
Second, the laying an aquatint ground of resin or copal upon a surface
of gelatine, and not as usual upon the makel metallic surface of the plate.

page_text: Third, after forming, a photographic image on gelatine, the heating it
strongly over a spirit lamp or otherwise.
Fourth, the use and employment of perchloride of iron as an etching liquid
for the production of photoglyphic engravings.
Fifth, the use and employment of the same as a substitute for aquafortis in
common etching.
In witness whereof, I, the said William Henry Fox Talbot, have here-
unto set my hand and seal, this Twenty-second day of September,
in the year of our Lord One thousand eight hundred and fifty-eight.
Witness,
JNO. ALCOCK.
W. 1. F. TALBOT. (L.S.)