Improvements in the Art of Producing Colored Photographs.
Year: 1892

page_text: Date of Application, 22nd Mar., 1892-Accepted, 10th Sept., 1892
COMPLETE SPECIFICATION.
Improvements in the Art of Producing Colored Photographs.
I, JAMES WILLIAM MCDONOUGH, of No. 1124 Monadnock Building, in the
City of Chicago, in the County of Cook, and State of Illinois, United States of
America, Gentleman, 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:-
My invention relates to the production of colored photographs, and may be
carried out in several different ways, one or two of which I will now set forth:
I take a plain glass plate and flow or cover it with a coat of varnish, or similar
material which will dry tacky. I then dust the plate with a mixture of colors
composed of fine or powdered particles containing the colors desired, and thus I
obtain a colored surface composed of particles lying side by side which have the
properties of stippled colors instead of the properties of a true mixture of
pigments.
In order to get these colored particles I may use powdered glass, transparent
pigments, gelatine, resin or shell-lac, stained by aniline dyes etc. The glass colors,
after having been dusted upon the surface of the dry plate, may be melted into the
plate, by fire, if desired.
In the preparation of a glass negative with shell-lac stained in colors, the plate
may be flowed or covered with a plain collodion, to which is added a small quantity
of glycerine, so that when the collodion is dry it will remain tacky enough to retain
colored shell-lac dust in a single layer. I then take a sufficient quantity of clean
white shell-lac, dissolved in alcohol, to which I add aniline colors, say, for one lot,
red and yellow colors in such proportions that the result will be a red which, when
viewed by transmitted light in thin layers, will cut off or absorb as much green,
blue and violet as possible, or which, in other words, will transmit as far as possible,
a pure red.
Another lot is colored with as pure a green as may be formed by
mixtures, adding yellow to absorb blue. Another lot is colored blue. As the
mixtures of colors formed in this way by red and green, do not form a bright yellow,
I may use in addition another lot colored as near the yellow of the spectrum as
possible. These lots, after being thus colored, are allowed to dry, forming colored
masses which are then reduced to powder by grinding sifting etc.
If now proper proportions of red and green are mixed, a nearly black mass will
be formed, and if proper proportions of red, green, yellow and blue, are mixed, a
mass will be formed that is nearly black; but if this same mixture is dusted or
thinly spread upon the prepared surface, it will reflect or transmit a mixture of all
these colors, which will be white in proportion to the purity of the color, cleanliness
of the mixture and the quantity of light transmitted or reflected. The glycerine
may be washed out so that only the colored particles in the masses in which they
are arranged, remain. When viewed under the microscope, the white surface is
seen to be composed of a multitude of different colored particles lying side by side,
and separated by small distances.
By subjecting the plate thus prepared to just sufficient heat to melt the shell-lac,
two results are obtained; first, the powdered particles melt and fill the gaps,
forming a surface which, when viewed in the microscope, resembles a window
formed of a mosaic of small colored pieces each adjoining the other, while if the
heat be carried further the edges melt into each other and further mixtures of
colors are obtained; second, the surface of the plate, which before heating reflects
all the colors and resembles the surface of ground glass, or glass covered with a
white powder in what is termed a matt surface, becomes, under the influence of
heat, transparent by the flattening of the particles. This result may also be

page_text: obtained in a measure by covering the surface with varnish so as to make it
smooth.
A plate formed in this way upon any suitable material may be flowed or covered
with such sensitive compounds as are used in taking photographs.
Instead of treating the glass plate with a coat of varnish or similar material
which will dry tacky, and then dusting such plate with a mixture of colors, as
above described, I may take a support of plain glass, celluloid, paper, or other
suitable substance upon the surface of which is a sensitive photographic coating,
preferably forming what is known as an orthochromatic dry plate. This may be
rendered tacky by immersing in water or diluted glycerine. If preferred, however,
the plate may be used before it gets quite dry in the course of its manufacture.
I dust the plate either while it is somewhat moist in the course of its manufacture,
or after it has become tacky as above explained, with a mixture of colors composed.
of fine or powdered particles containing the colors desired. The particles, however,
may, if preferred, be applied in other ways so long as the same result is secured.
I thus obtain a colored surface composed of particles lying side by side which have
the properties of stippled colors as above explained. In the latter of the methods
of forming the plate above described, after the colors are applied, the surface may
be flowed with a thin coat of gelatine which will penetrate the spaces between the
colored particles, or the ground and colored particles may be coated with gelatine
before applying them to the tacky surface by mixing them with a small quantity.
of dissolved gelatine, and re-grinding them, according as a matt or smooth surface
is required.
The process of producing the effect called color above described is by absorption
of light, but inasmuch as color effects may be produced by refraction, dispersion
or diffraction of light, I do not mean to limit myself. to absorption only as the
means of producing them.
The photographic plate thus obtained, consisting of colored particles applied to
its sensitive surface, may be exposed to the action of the light from the object to be
photographed, through a camera, in such manner that this light will pass through
the colored particles and affect the sensitive film, thus producing a latent image of
the object.
The plate may then be developed by the use of the so-called alkaline-developer,
so that the colored particles will adhere to the surface which is penetrated by the
same colored light as the particles themselves, because gelatine is rendered
insoluble in proximity to the silver bromide particles in the sensitive compound
where acted upon by light. Thus particles which do not allow the passage of
colored rays, on account of absorption, may be washed off because as to such
particles the gelatine remains soluble. Thus blue rays will cause blue particles to
remain as an image; white light, all the colored particles in that space acted upon
by white light; and all will be removed where black occurs; which does not act
upon the photographic film. After the development, the picture may be treated
with thio-sulphate of soda to remove the sensitive compound not acted on by the
light and developer. By thus developing the plate a picture composed of the
particles of silver and the colored particles remaining on the plate after
the development, is produced.
The use of orthochromatic dry plates and colored screens before the camera for
the purpose of sifting light and regulating the action of different colors upon the
film is too well known to require explanation. I will merely add that the particles
are dusted, spread or placed upon the plate in such proportions as to produce a
white or transparent surface.
It is obvious that many variations may be made in the details of my invention
without departing from the spirit thereof.
Having now particularly described and ascertained the nature of my invention
and in what manner the same is to be performed, I declare that what I claim is:
1.-The process of preparing photographic plates, which consists in covering

page_text: them with colored particles, and then applying a sensitive compound to them,
substantially as and for the purpose set forth.
2. The process of preparing photographic plates, which consists in covering
them with colored particles, then subjecting them to heat, and then applying a
sensitive compound to them, substantially as described.
3. A plate for photographic purposes having upon its surface a layer of different
colored particles lying side by side, and in such proportions as to produce a white
or light colored transparent surface to which may be applied a sensitive compound,
substantially as described.
4.-A. plate for photographic purposes formed of glass or other suitable material
-of any color, a layer of different colored particles spread thereon, and a film of
sensitive photographic compound spread over the particles, substantially as
described.
5. The process of preparing photographic plates which consists in applying a
sensitive compound to them and then covering them with colored particles;
substantially as described.
6.-The process of preparing photographic plates which consist in applying to
their sensitive surface particles of glass or other substances which show colors by
absorption, refraction, dispersion or diffraction; substantially as described.
7. The process of preparing photographic plates and pictures which consists in
applying a sensitive compound to them, covering them with colored particles lying
side by side in such proportions as to produce a white or light colored transparent
surface, and then washing out such particles as are not acted upon by light;
substantially as described.
8. A plate for photographic purposes having a sensitive surface to which is
applied a layer of different colored particles lying side by side and in such
proportion as to produce a white or light colored transparent surface; substan-
tially as described.
Dated, at Chicago, in the County of Cook and State of Illinois, United States
of America, this 27th day of January 1892.
JAMES WILLIAM MCDONOUGH.