IMPROVE- MENTS IN THE ART OF ENGRAVING
Year: 1852

page_text: LETTERS PATENT to William Henry Fox Talbot, of Lacock Abbey,
in the County of Wilts, Esquire. for the Invention of "IMPROVE-
MENTS IN THE ART OF ENGRAVING."
Sealed the 24th January 1853. and dated the 29th October 1832.
PROVISIONAL SPECIFICATION left by the said William Henry
Fox Talbot at the Office of the Commissioners of Patents, with
his Petition. on the 29th October 1852.
I, WILLIAM HENRY FOX TALBOT, of Lacock Abbey. in the County
of Wilts, Esquire, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE ART OF ENGRAVING," to be as follows:-
The metallic plate which is to be engraved is first coated or covered
with a substance which is easily changed or altered by being exposed
10 the light of the sun or to daylight. Then, by the methods which are
employed in the art of photography, an image or picture is formed by
the light acting upon the coating of the plate. This being done.
chemical substances are employed which have the property of etching
or biting into the metallic plate in those places only which have been
protected from the light, or upon which the light has not acted strongly.
The plate is then washed and cleaned. and then its surface exhibits a

page_text: distinct elching or engraving resembling the picture or image which
was originally formed upon it. Copies are then struck off from the
engraved plate in the usual way of copper plate or steel plate printing.
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 29th April 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME. I.
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-ninth day of October. in the
year of our Lord One thousand eight hundred and fifty-two. in the
sixteenth 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
1. 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
signs, 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, by an instrument in writing under my
hand and seal. should particularly describe and ascertain the nature of
the said Invention. and in what manner 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

page_text: manner the same is to be performed. to be particularly described and
ascertained in and by the following statement thereof (that is to say):
The metallic plate which is to be engraved is first coated or covered
with a substance which is easily changed or altered by being exposed
to the light of the sun or to daylight. Then, by the methods which are
employed in the art of photography, an image or picture is formed by
the light acting upon the coating of the plate. This being done,
chemical substances are employed which have the property of etching or
biting into the metallic plate in those places only which have been pro-
tected from the light, or upon which the light has not acted strongly.
The plate is then washed and cleaned. and then its surface exhibits
a distinct etching or engraving resembling the picture or image which
was originally formed upon it; copies are then struck off from the
engraved plate in the usual way of copper plate or steel plate printing.
The particular methods by which this photographic etching of the plate
is effected are believed to be entirely new.
Having thus given in my Provisional Specification a general outline
of my Invention, I now proceed to describe more particularly the
details of the process.
The following is my method of engraving steel plates. 1 take a
good steel plate prepared as it usually is for the use of engravers: and,
first, I dip it for a minute or two into vinegar acidulated with a little
sulphuric acid, then wash it and wipe it quite clean and dry. Then I
prepare a solution of gelatine or common isinglass in water. It should
be made of moderate strength, such as when cold coagulates into a
firm jelly.
Having warmed this solution, and strained it through a
linen cloth, add to it about half its volume of a saturated solution of
bichromate of potash in cold water, and stir the mixture well. This
nixture is to be kept moderately warm while in use to prevent its
coagulation; and since this warmth causes it gradually to part with its
water, and grow thicker or more viscid. therefore it is necessary that
the operator should from time to time add so much water as he judges
ecessary to replace what has been lost. The steel plate being first
lightly warmed. I pour some of the prepared gelatine upon it, and
with a glass rod held horizontally I spread it over the whole plate. l

page_text: I then
I
then incline the plate. and pour off the superfinons gelatine.
place it on a stand. which should be kept as nearly horizontal as pos-
sible to prevent the gelatine from flowing to one side of the plate.
then place a spirit lamp beneath the plate, and warm it gently till the
gelatine is dry. This process should not be performed in very strong
daylight, because the prepared gelatine would be injured by the light.
The film of prepared gelatine, when properly dried upon the steel. has
If too much
an uniform bright yellow colour. and a smooth surface.
bichromate is employed in proportion to the gelatine, the surface of the
dried film appears clouded in various parts, owing to the formation of
minute crystals. This defect is easily remedied by adding some more
fresh gelatine to the mixture. After a little practice the operator will
When the steel plate
have no difficulty in obtaining a uniform film.
has been in this manner coated with a regular and uniform film of
prepared gelatine, it is ready to receive a photographic image of the
object which is intended to be engraved. I will suppose, in the first
place, that the object is capable of being applied in close contact with
the surface of the prepared steel plate; for example, a piece of lace. or
the leaf of a plant. I place the object upon the steel plate; then a
sheet of glass is laid over it, and screwed into close contact with it,
which is best done by means of what is commonly called a photo-
graphic copying frame.
The plate is then to be exposed to the sun's
rays for a certain time. varying according to circumstances from half a
minute to five minutes or more, until the operator judges that a sufli-
The effect of the sun's rays
ciently strong image has been produced.
is to turn the colour of the plate from yellow to brown, but the parts
shaded or protected by the object of course retain their original yellow.
the result is therefore the formation of a yellow image of the object
upon a ground of a brown colour. The plate is then taken out of the
frame, and the object being removed from it. it is seen whether a good
image has been obtained. In that rase the operator proceeds as
follows: The plate is taken and dipt into cold water for one or two
minutes, which removes all the bichromate of potash, and the greater
part of the gelatine also. from the parts of the plate upon which the
sun's rays have not acted, while on the contrary it removes but little

page_text: from those parts which have been fully exposed to the sunshine: the
consequence of this is that the image is whitened. The plate is then
removed from the water, and dipped into alcohol for one minute. It is
then removed, and placed in a vertical position in some warm place.
and in the course of a few minutes it becomes entirely dry. This
completes the photographic part of the process: and the plate is.
generally speaking. now seen to be impressed with a white image of
the object, often very perfect and beautiful, placed upon a ground of a
brown on brownish yellow color.
It now remains to etch the photographic image thus obtained.
For that purpose take some bichloride of platina. containing a
little free acid. and dissolve it in cold water. taking care that the
solution is quite saturated. I then add to four parts of this satu-
rated solution one part of water. This part of the process requires
attention. for if the quantity of water is in a material degree either
too great or too little, the etching process is liable to failure. The
best way is to proceed experimentally by adding water gradually to
a considerable quantity of the saturated solution, and making trial
of the results until they become satisfactory. When this is at-
tained the solution is to be kept in a well stoppered bottle for im-
mediate use at any time. A solution of the proper strength having
been carefully prepared and tested as above mentioned, the etching
process is executed as follows:-The plate is laid horizontally on a
table, and a small portion of the platina solution is poured upon it, and
quickly diffused and spread over the whole plate with a camel's hair
brush. It is hardly necessary to surround the plate with a wall of wax.
as practiced by engravers in the usual mode of etching copper plates,
although this may be done if preferred. But the liquid does not often
flow off the plate. in consequence of the small quantity of it which is
used. If a greater depth of it were poured on, it would, from its great
pacity, prevent the operator from discerning the effects produced by it
upon the plate of metal. The platina solution then being poured on the
plate it produces no effervercence or escape of gas, but in the course of a
minute or two the whole photographic image of the object which existed
upon the steel plate is seen to blacken, and when this change is com-

page_text: plete there is seen a very distinct and regular black image of the object.
The operator watches until it has a satisfactory appearance to his eye.
and looks finished, or as perfect as he judges it likely to become, which
generally happens in one or two minutes. When he thinks it is finished.
or not likely to be further improved or developed, he inclines the steel
plate gently, and pour off the platina solution by one corner of the plate
into a bottle placed to receive it: the surface of the plate is then dried
with blotting paper. and then a stream of water. or. what is better, a
strong solution of salt in water. is poured over the plate, which carries
off the remainder of the platina solution. The plate is then rubbed
with a wet sponge or linen cloth. which, in a short time, detaches and
removes the film of gelatine from the steel. and enables the operator
to see the etching which has been obtained. The plate ought then to
be coated with wax. because a newly prepared etching is very easily
oxidated or rusted by the atmospheric air. Impressions can be printed
off from the steel plate thus engraved in the mode usually employed by
copper plate and steel plate printers.
When the etched parts are both broad and uniform. as in the case,
for instance, when the object is an opaque leaf of a plant, although
the etching holds the ink pretty well. yet when printed off. the
effect is not always satisfactory. | proceed therefore to explain a
useful modification of the process. In order to which I must observe
that when the object placed on the steel plate to be engraved is a piece
of black crape or gauze, an engraving of it is obtained in the way
above mentioned, which truly depicts the object, representing every
thread in its proper place by a corresponding engraved line: but when
two or three thicknesses of this gauze are employed instead of one. and
are placed obliquely to each other at various angles, then the resulting
engraving offers a mass of lines intersecting each other in different
directions which cover the hole plate. and which, when printed off
upon paper. produce a result which, to an eye at a little distance.
appears like a uniform shading. Now let its suppose that we have in
this way covered a prepared steel plate with two or three folds of black
crape or gauze. and placed it in the sunshine. When taken out of the
sunshine and the crape removed. let the broad leat of a plant, or some

page_text: other object of irregular outline. be placed upon the centre of the plate,
and then let the plate be replaced in the sunshine for three or four
minutes. When it is removed for the second time. and the object
detached, it will be seen that the light of the sun acting upon the parts of
the plate exterior to the object has wholly obliterated the previous effect
produced by the gauze, and has converted that part of the plate to a
uniform brown colour, while the central part of the plate offers, the
image of the leaf, upon which the crowded intersecting lines produced
by the gauze are still seen. The plate is now to be etched as
previously described. and the result is. that an etching of a leaf is
produced covered with engraved lines, which lines are entirely wanting
on the rest of the plate. When this is printed off. the impressions
offer the appearance of a leaf nearly uniformly shaded. But in order
to obtain greater perfection in this respect, it is only necessary either to
manufacture on purpose some pieces of more delicately woven fabrics.
or to cover a sheet of glass by any convenient method with fine opaque
lines to intercept the light. or with a powder adhering to the glass.
consisting of distinct opaque particles, and very uniformly diffused over
the surface. These things, which I believe have not been heretofore
nsed in the fine arts. I would denominate photographic screens or veils.
Another method is to cover the steel plate with an aqua-tint ground,
consisting of particles of resin. before coating it with the gelatine; but
in that case the dipping of the plate into alcohol, which occurs in the
foregoing description of my process. must be omitted: and morcover.
a fresh aqua-tint ground requires to be laid upon every plate: whereas
a single veil, such as I have above described, serves for any number of
plates in succession. The method of engraving which I have here
described as applied to steel plates is also applicable to plates of zinc.
Lithographic stones are also readily engraved by the same process.
When the object to be engraved is not of a nature to be placed in
contact with the steel plate, it is necessary first to form a negative
photographic image of it on paper or on glass by the usual methods
employed in photography: then to make from this negative photograph
a positive copy. either upon glass or upon paper of good uniform texture
and moderately transparent; and. lastly. to put this positive copy in

page_text: close contact with the steel plate, and then to place the plate in the
sun's rays, when it will take an image of the object, as above described.
The prepared steel plate may also be placed in the focus of a camera,
and the camera directed to the object. but as the film of prepared
gelatine is not very sensitive to feeble lights this process in general
would occupy a considerable time.
I have stated that I employ in this process a solution of gelatine
mixed with bichromate of potash, but I do not confine myself to the
use of gelatine. Other substances may be used, especially albumen or
white of egg. and gum arabic, or mixtures of these, and other analogous
substances in various proportions. But notwithstanding that I have
found some of these mixtures to afford good results, yet on the whole
I think it answers best to employ only gelatine mixed with the bi-
chromate of potash: and throughout this Specification I have used for
brevity the term "gelatine." to denote a solution of isinglass in water.
carefully strained and made as free from impurities as possible. And
I have used the terms positive and negative as they are usually em
ployed in the science of photography. I have described the solution
of platina which seems to me the best, but I do not confine myself 10
this etching liquid. Other liquids may he employed capable of etching
surfaces of metal or stone. provided they possess the essential quality
of not penetrating the film of prepared gelatine which cover the portions
of the surface not intended to be etched.
The processes described in this Specification which claim to be new
Inventions are. -
First. the producing or obtaining etchings or engravings by photo-
graphic and chemical means alone upon plates of steel.
Second, the method described of covering surfaces of metal or stone
with a coating of gelatine, rendered sensitive to the action of light by
being mixed with a solution of bichromate of potash or other liquid
which possesses photographic properties, and which unites freely with
gelatine. producing, when the gelatine is dried, a coating sensitive
to light, and which by the action of the solar rays upon it becomes
either less soluble in water than before, or altogether insoluble in tha
liquid.

page_text: Third, the removal by the action of water of the more soluble parts
of the photographic image, for the purpose of rendering them permeable
to an etching liquid.
Fourth, the employing a chemical liquid for the purpose of etching
the surface upon which the photographic image has been formed, as
above mentioned, which liquid possesses the requisite etching property.
but has not the property of penetrating the coating of gelatine which
covers and protects the portions of the surface not intended to be
etched.
And whereas in reciting these claims I use for brevity the word
gelatine," and I have already stated that albumen and gum possess
analogous properties; I would therefore be understood to include them
in my claim as being capable of replacing the gelatine in the above
described process.
Fifth, the employing an apparatus for partially intercepting the sun's
rays, which in my present Specification I have called a photographic
screen or veil, for the purpose of producing a change or alteration in
the final character of the etching.
In witness whereof, I, the said William Henry Fox Talbot, have
hereunto set my hand and seal, this Twenty-third day of April,
in the year of our Lord One thousand eight hundred and
fifty-three.
5
Witness,
S. CARPMAEL.
W. H. F. TALBOT. (...)