Improvements in Photography.
Year: 1891

page_text: Date of Application, 19th May, 1891-Accepted, 4th July, 1891
Improvements in Photography.
A communication from Joux NORTH, of New York, in the County and State of
New York, United States of America, Inventor.
I, ALFRED JULIUS BOULT, of 323 High Holborn in the County of Middlesex,
M.I.M.E., do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:―
The invention has reference to a new process of producing photographs, images
and pictures on hard surfaces, as glass, metal, porcelain &c. and the invention
consists in applying to such a surface a coating of a solution of guaiaretic acid, or of
the guaiaretate of a metal or organic base and submitting the so coated surface under
a photographic negative or a transparent positive of the image to the action of
light, whereby the parts of the coating exposed to the light through the unaffected
parts of the negative or transparent positive become hard and insoluble, then
developing the coated surface and finally applying to the film a suitable acid,
whereby the picture is etched into the surface. The hard portions of the film which
are not affected by the acid are then removed and the etched plates, if desired,
blackened by means of a suitable pigment. If coloured glass pictures are to be
produced, the so prepared surface of the glass-plate is painted with the desired
colours, which are burned into the glass-plate.
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It has been found that the guaiaretic acid (C H, O.) or its metallic salts, or
those made of guaiaretic acid with organic bases, by exposure to light, change their
properties as to solubility, and as to resistance to oxidizing agents.
The guaiaretic acid, as well known, is freshly prepared, soluble in alcohol, ether,
bisulphide of carbon, chloroform, acetic acid, benzole, and other substances, but, by
exposure to light, it becomes less or entirely insoluble in these substances, like
asphaltum or resinates, that is to say the salts of abietic acid (CHO). As
far as the researches go, guaiaconic acid (C₁, H2 O) is formed by this action,
which latter is still more oxidized by certain likewise acting substances. A similar
effect takes place by exposing the salts of guaiarctic acid with metals or organic
bases, also the chlorine, bronine, and iodine substitution products or the corresponding
salts, to the action of light.
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Certain colours, for instance aniline violet, magenta red, safranine, when
combined in minute quantities with guaiaretic acid or its salts, accelerate the action
of the light, i.e. they act as sensitizers. A thin coating of this acid or its salts,
laid upon a hard surface and exposed to the light for a certain time, becomes
impermeable to dilute mineral or organic acids. These properties of guaiaretic
acid or its salts, as aforesaid, render them useful for the production or reproduction
of pictures, photographs, ornaments, i.e. by means of the actinic rays.
In carrying out this invention to produce a photographic picture, image, or
ornaments on a hard surface, as metal, porcelain glass lithographic stone &c. I first
dissolve 100 parts of crystallized guaiaretic acid, or, to obtain a more sensitive film,
of 120 parts of dry amorphous guaiaretate of silver or of a corresponding quantity
of the zinc, lead, or magnesium-salt (which latter are less sensitive than the silver
salt) in 500 parts of pure benzole. I may use the salts colored with 3 to 4 per cent.
of aniline violet or another aniline color or colors. I then prepare a rubber solution
by dissolving 7 parts of dry caoutchouc in 500 parts of benzole. Instead of rubber
or gutta-percha a collodion solution containing 1 to 2 per cent. of nitro cellulose
may be used but I prefer the above described composition of rubber.
Both solutions are then thoroughly mixed together and the well-cleaned surface

page_text: on which the picture is to be produced is carefully coated with the mixture, thus
obtained, in the dark. Then the so-coated surface is exposed under a negative or
transparent positive to the action of light, a 10 to 12 minutes' exposure to direct
sunlight being sufficient to harden the exposed parts and to render them insoluble
in the developing bath. As the best bath for this purpose I use a mixture of one
part of benzole and 5 parts of spirits of turpentine. Of course other developers
can be used. The parts of the film which are not affected by the action of the
light, are thereby removed and the picture appears on the surface. The plate is
then dried and etched by appropriate acids according to the nature of the surface
to which the sensitive film is applied. Another method of applying the light
sensitive properties of the guaiaretic acid or of the guaiaretates to the art of
production of pictures, images or ornaments is the following;-
I mix a neutral aqueous solution of 10 parts of guaiaretic acid in any alkali with
100 parts of a dilute solution of gelatine; then 1 coat the well cleaned surface with
this solution and dry it in the dark in a horizontal position by a heat not exceeding
120° F. The object is then put into a tray containing a weak solution of sulphuric,
hydrochloric or any other suitable acid to precipitate the guaiaretic acid in the
gelatine film or in a weak solution of a salt of a metal for instance of nitrate of
silver sulphate of magnesium &c. to form a guaiaretate. The film can be more
sensitized if it is brought after thoroughly washing, in a very dilute bath of an
aniline color, as above mentioned. After a second drying the film is exposed under
the negative or transparent positive and developed by means of a benzole developer.
The gelatine film is then after drying hardened by chromic or common alum, tannic
acid or any other suitable substance. The surface is then etched in the manner
described. If the picture is produced on a lithographic stone or on a metal-plate
the stone or metal-plate can be used as a printing plate.
If it is desired to produce a colored glass picture the etching produced on the
glass plate according to the described process is rubbed in with a black pigment
and the plate burned whereby the fundamental picture is fixed on the glass plate
in lines or halftone. The color powders or color mixtures as used in the art of
glass-painting are then applied to the fundamental picture and the glass plate then
burned in a muffle-furnace.
The glass pictures produced by this method have a highly attractive appearance
as the etched and blackened background imparts to the same an effective and
natural expression.
The guaiaretic acid which I use is prepared in the following way ;--2 parts of
guaiacum are dissolved in 10 parts of alcohol filtered and concentrated to a thin
syrupy solution, then it is mixed with a warm concentrated solution of 1 part of
potassium hydrate. After 24 hours standing the mixture forms a muss of the
consistency of a pulp and is pressed through a filtering cloth. The remainder is
thoroughly washed first with alcohol and then with water and crystallized by means
of dilute alcohol.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is ;-
1. The process of producing photographs images and pictures on hard surfaces
which consists in coating the surfaces with a solution of guaiaretic acid or of the
guaiaretate of a metal or organic base subjecting the so coated surface under a
negative or transparent positive to the action of the light and after developing the
same subjecting the surface to a suitable acid by which the photograph or image is
etched into the surface substantially as set forth.
2. The method of producing colored glass pictures by subjecting the glass plate
coated with a solution of guaiaretic acid or of the guaiaretate of a metal or organic
base under a negative or transparent positive to the action of light and after
developing the same subjecting the surface to a suitable acid then blackening the
etched parts of the glass plate with a suitable pigment and burning the plate then

page_text: applying to the picture in lines or halftone thus produced the desired colors and
finally burning the colors into the glass plate substantially as set forth.
3. In the art of photography the employment of guaiaretic acid or its metal or
organic salts as the essential sensitizing medium substantially as set forth.
4. As a new article of manufacture a photograph made by means of guniaretates
or guaiaretic acid substantially as set forth.
Dated the 10th day of Max 1801
W. P. THOMPSON & BOULT,
Agents for the Applicant.