An Improved Photographic Process Giving, without Transfer, Images with their Half Tints, and the Application of this Process to Photography in Colors.
Year: 1895

page_text: Date of Application, 8th Apr., 1895
Complete Specification Left, 13th Dec., 1895-Accepted, 18th Jan., 1896
PROVISIONAL SPECIFICATION.
An Improved Photographic Process Giving, without Transfer,
Images with their Half Tints, and the Application of this
Process to Photography in Colors.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings in the
County of London, Patent Agent, do hereby declare the nature of this invention,
a communication to me from Auguste Luniière and Louis Lumière both of
21, 23 and 25 Rue Saint Victor Lyon-Montplaisir in the Republic of France,
Manufacturers of Photographic Products and Materials, to be as follows:-
==
As is well known Messrs. Cros and Ducos du Hauron's method of photo-
graphically obtaining colors, consists in producing three negatives of the same
object, each negative representing the negative image of the red, yellow and blue
radiations emitted or reflected by the said object. Each of these negatives being
then used for obtaining a monochrome image in either red, yellow or blue. The
superposition of these three monochromes reconstitute therefore the colors of the
original.
This process has not hitherto been practically adopted as the obtaining and
superposition of monochromes have presented great difficulties.
This result has nevertheless been accomplished by the communicators by the
employment of the photographic process using bicromated mucilages.
They have remarked that coldly soluble glue bicromated, which does not give
the demi-tints when it is employed alone acquires this property when insoluble
substances are added to it under certain conditions. If for example to a ten per
cent. solution of glue, there is added about five per cent. of bichromate of ammonia
and from about five to ten per cent. of bromide of silver emulsion, and that this
preparation is spread in a thin layer upon a glass plate, there is obtained a sensitive.
surface which is exposed to light under the negative to be reproduced. When it
has been sufficiently exposed, the plate is washed in cold water and there is thus
obtained an image scarcely visible furnished by the glue which has been rendered
insoluble and which can be colored with suitably chosen coloring matters.
The bromide of silver is removed by a suitable solvent, hyposulphite of soda for
example.
•
This process gives, with the greatest facility, negatives of all the colors with all
the graduations of tints of the negative..
The coloring matter can also be added before spreading the sensitive substance
on the glass or other support and a complete negative obtained by simple washing
in cold water.
Glue may be replaced by other mucilages soluble in a cold state or even by
gelatine.
In this latter case it is advisable to develope in tepid water.
The bromide of silver can also be replaced by starch or other precipitate which
is then dissolved in a suitable solvent.
With such a process, it is easy to produce polychrome images, by utilizing the
principle of Messrs. Cros and Ducos du Hauron's process.
For this purpose
I proceed to obtain successively upon one and the same plate, three monochrome
images, red blue and yellow arising from the three corresponding negatives, taking
care to isolate cach image from the preceding one, by one or several impermeable
coatings, of collodion or of caoutchouc for example.

page_text: This method presents the following advantages which render the photography of
colors absolutely practical, if, be it understood, the negatives are well executed.
1st. Facility and simplicity of manipulations.
2nd. Possibility of varying the relative intensity of the monochromes, by a
simple decoloration by water or by the employment of more or less concentrated
coloring matters.
3rd. Possibility of readily modifying the effect of the three first layers, by the
addition of a fourth, or a fifth or even more.
4th. Very easy and perfect register.
5th. Possibility of transferring to paper the entirety of these impressions.
An Improved Photographic Process Giving, without Transfer,
Images with their Half Tints, and the Application of this
Process to Photography in Colors.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings in the
County of London, Patent Agent, do hereby declare the nature of this invention,
a communication to me from Auguste Lumière and Louis Lumière both of
21, 23 and 25 Rue Saint Victor Lyon-Montplaisir in the Republic of France,
Manufacturers of Photographic Products and Materials, and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement :-
As is well known Messrs. Cros and Ducos du Hauron's method of photo-
graphically obtaining colors, consists in producing three negatives of the same
object, each negative representing the negative image of the red, yellow and blue
radiations emitted or reflected by the said object. Each of these negatives being
then used for obtaining a monochrome image in either red, yellow or blue. The
superposition of these three monochromes reconstitute therefore the colors of the
original.
This process has not hitherto been practically adopted as the obtaining and
superposition of monochromes have presented great difficulties.
This result has nevertheless been accomplished by the communicators by the
employment of the following photographic process using bicromated mucilages.
They have remarked that bichromated glue soluble in a cold state which does
not give the demi-tints when it is employed alone, acquires this property when
insoluble substances are added to it under certain conditions. If for example to a
ten per cent. solution of glue, there is added about five per cent. of bichromate of
ammonia and from about five to ten per cent. of bromide of silver emulsion, and
that this preparation is spread in a thin layer upon a glass plate, there is obtained
a sensitive surface which is exposed to light under the negative to be re-produced.
When it has been sufficiently exposed, the plate is washed in cold water and there
is thus obtained an image scarcely visible, furnished by the glue which has been
rendered insoluble and which can be colored with suitably chosen coloring matters.
The bromide of silver is removed by a suitable solvent, hyposulphite of soda for
example.
This process gives, with the greatest facility positives of all the colors with all
the graduations of tints of the negative.
The coloring matter can also be added before spreading the sensitive substance
on the glass or other support and a complete positive obtained by simple washing
in cold water.

page_text: Glue may
gelatine.
In this latter case it is advisable to develope in tepid water.
be replaced by other mucilages soluble in a cold state or even by
The bromide of silver can also be replaced by an insoluble precipitate such as
starch which remains in the layer of preparation or by another precipitate capable
of being afterwards dissolved in a suitable solvent.
With such a process, it is easy to produce polychrome images, by utilizing the
principle of Messrs. Cros & Ducos du Hauron's process.
For this purpose I proceed to obtain successively upon one and the same plate,
three monochrome images red, blue and yellow arising from the three corresponding
negatives, taking care to isolate each image from the preceding one, by one or
several impermeable coatings, of collodion or of caoutchouc for example.
This method presents the following advantages which render the photography
of colors absolutely practical, if, be it understood, the negatives are well executed.
1st. Facility and simplicity of manipulations.
2nd. Possibility of varying the relative intensity of the monochromes, by a
simple decoloration by water or by the employment of more or less concentrated
coloring matters.
3rd. Possibility of readily modifying the effect of the three first layers by the
addition of a fourth, or a fifth or even more.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The employment of bichromated mucilages soluble in a cold state to which
suitable insoluble substances are added, for the production of photographic images
without transfer, with all their demi-tints, these substances being afterwards
eliminated by suitable solvents or allowed to remain in the layer substantially as
herein described.
2. In the photographic process herein described, the employment of gelatine
and other mucilages soluble in luke warm or tepid water substantially as herein
described.
3. The employment of the process without transfer herein described for obtaining
proofs in colors upon glass, paper or other support by the successive impression on
the same plate of three monochrome images obtained from three negatives
substantially as herein described.
4. In the production of photographs in colors the employment of the process
herein described.
Dated December 13th 1895.
HARRIS & MILLS,
23 Southampton Buildings, London, W.C., Agents.