IMPROVEMENTS IN PHOTO-TYPOGRAPHY.
Year: 1879

page_text: LETTERS PATENT to Charles Guillaume Petit, Photographic Artist, of the
City of Paris, in the Republic of France, for the Invention of "IMPROVEMENTS
IN PHOTO-TYPOGRAPHY.
"
Sealed the 11th May 1880, and dated the 21st November 1879.
PROVISIONAL SPECIFICATION left by the said Charles Guillaume Petit at
the Office of the Commissioners of Patents on the 21st November 1879.
CHARLES GUILLAUME PETIT, Photographic Artist, of the City of Paris, in the
Republic of France. "IMPROVEMENTS IN PHOTO-TYPOGRAPHY."
The object of the present Invention is to transfer a half shade plate taken from
nature to a lined plate forming a typographic relief. One of the characteristic
properties of a layer of bichromated gelatin when exposed for a certain time beneath
a photographic plate in the midst of actinic light is that it resists expansion when
immersed in cold water in proportion to the amount of light it receives, and this
peculiar property is utilized for producing images from this plate in relivo or
intaglio.
Another peculiarity of this layer of gelatin is that it also resists solution in warm
water in proportion to the light received, and hence images in relief and hollow
can be produced. The only difference between the two is that in the first case a
positive is required for the blacks of the plate forming relief, and in the second
case a negative is used. A white or photogenic substance, such, for example, as
wax, susceptible of delicately receiving the impression of the gelatin thus prepared
is employed.
This operation done the surface of the modeling is rendered antiphotogenic by
blacking it as superficially as possible with black lead, for example. The modeling
thus prepared is placed in an engraving or etching machine in such a position that
the point of the tool, which is V shaped, can make incisions on the surface in a
precise and rigorously mathematical manner. The following then occurs :-
The maximum of penetration of the point of the tool in making an incision is
regulated on the deepest hollows of the modeling by sparing all the large hollows
and cuts the reliefs in proportion to their height. At the second incision, whose
proximity to the first is regulated on the highest reliefs, like the first spares the

page_text: greatest hollows and cuts the reliefs in such a manner as to meet the incision made
by its preceding course only on the highest, and so to remove all the anti-photogenic
matter with which they were covered.
Thus by the successive incisions of the tool well regulated in depth, in proximity
to each other and in intersection, an image is formed on the surface of the moulding
which properly lighted and photographed reproduces the original plate in a plate
formed solely of perfect whites and blacks; that is to say, useful for all kinds of
printing reproducing the characteristics of the original subject, especially applicable
to photography.
For the sake of shortening the operation above mentioned, which may be
considered as an analysis of the process, by engraving the surface of the wax before
modeling, or by the simple use of a greasy paper, or bearing the dry impression of
the several combinations of hollow lines, the modeling is then performed in the
following manner:-After having selected a wax or paper on which the depth of
the cutting is equivalent to the highest reliefs of the gelatin the paper or wax is
placed on a hard and perfectly even surface. Above this is placed the gelatin
uniformly and as superficially blacked as possible, and then another smooth hard
surface. The whole is then submitted to pressure, and the wax or paper, as the
case may be, will each carry in all the lines of their surfaces as much more black
(deposited on the gelatin) in proportion as the lines or grain have been more or less
flattened by the reliefs of the gelatin. By this means an image is formed of black
and white lines, the depths of colour being proportionate to the reliefs of the gelatio,
which image re-photographed produces a plate capable of serving as a typographic
relief.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Guillaume Petit in the Great Seal Patent Office on the 17th
May 1880.
CHARLES GUILLAUME PETIT, Photographic Artist, of the City of Paris, in the
Republic of France. "IMPROVEMENTS IN PHOTO-TYPOGRAPHY."
The object of this Invention is to transform a half shade plate taken from nature
to a lined plate forming a typographic relief.
One of the characteristic properties of a layer of bicromated gelatin when
exposed for a certain time beneath a photographic plate in the midst of actinic
light is that it resists expansion when immersed in cold water in proportion to the
amount of light it receives, and this peculiar property is utilized for producing
images from this plate in relivo or intaglio.
Another peculiarity of this layer of gelatin is that it also resists solution in warm
water in proportion to the light received, and hence images in relief and hollow
can be produced. The only difference between the two is, that in the first case a
positive is required for the blacks of the plate forming relief, and in the second case
a negative is used.
A white or photogenic substance, such, for example, as wax, susceptible of
delicately receiving the impression of the gelatin thus prepared is employed.
This operation done the surface of the modeling is rendered antiphotogenic by
blacking it as superficially as possible with black lead; for example, the modeling
thus prepared is placed in an engraving or etching machine in such a position that
the point of the tool, which is V shaped, can make incisions on the surface in a
precise and rigorously mathematical manner. The following then occurs:-
The maximum of penetration is regulated on the deepest hollows of the modeling
by sparing all the large hollows and cuts the reliefs in proportion to their height.
At the second incision, whose proximity to the first is regulated on the highest
reliefs, like the first spares the greatest hollows and cuts the reliefs in such a
manner as to meet the incision made by its preceding course only on the highest,
and so to remove all the antiphotogenic matter with which they were covered.
Thus by the successive incisions of the tool well regulated in depth, in proximity
to each other and in intersection, an image is formed on the surface of the modeling
which properly lighted and photographed reproduces the original plate in a plate
formed solely of perfect whites and blacks; that is to say, useful for all kinds of
printing reproducing the characteristics of the original subject, especially applicable
to typography.
The principal of the Invention, or the transformation of an ordinary photographic
plate into one formed of white and black lines or points in proportion to the size of
the relief obtained by chemical combinations which are rendered insoluble by light,
may also be effected as follows:-For the sake of shortening the operations above
mentioned, which may be considered as an analysis of the process, by engraving
the surface of the wax before modeling, or by the simple use of grained paper, or
bearing the dry impression of the several combinations of hollow lines, the modeling
is then performed in the following manner :--
After having selected a wax or paper on which the depth of the cuttings is
equivalent to the highest reliefs of the gelatine the paper or wax is placed on a
hard and perfectly even surface. Above this is placed the gelatin uniformly and as
superficially blacked as possible, and then another smooth hard surface. The whole
is then submitted to pressure, and the wax or paper, as the case may be, will each
carry in all the lines of their surface as much more black (deposited on the gelatin)
in proportion as these lines or grain have been more or less flattened by the reliefs
of the gelatin.

page_text: By this means an image is formed of black and white lines, the depths of colour
being proportionate to the reliefs of the gelatin, which image rephotographed pro-
duces a plate capable of serving as a typographic relief in the manner and by the
means specified.
I claim, the transformation of a half shade plate taken from nature to a lined
plate forming a typographic relief.
In witness whereof, I, the said Charles Guillaume Petit, have hereunto set my
hand and seal, this Twelfth day of May, in the year of our Lord One
thousand eight hundred and eighty.
CHARLES GUILLAUME PETIT. (LS.)