Process for Producing Coloured Photographs.
Year: 1892

page_text: The decision of the Comptroller-General, of the 14th day of January 1895,
allowed, under Section 18 of the Patents, &c. Act, 1883, an Amendment
of this Specification.
Date of Application, 1st Apr., 1892-Accepted, 4th Jun... 1892
COMPLETE SPECIFICATION (AMENDED).
Process for Producing Coloured Photographs.
I, VICTOR MATHIEU of 9 Agincourt Road West Hampstead, London,
Photographer do hereby declare the nature of my said invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
According to this invention I produce, by the aid of the sunlight or of strong
artificial light, photographic negatives of such a character that prints made
therefrom on sensitized paper, glass, gelatine film, thin skin or other suitable
material shall be capable of receiving colouring in such manner as to resemble
perfectly the objects photographed.
When working by the sunlight, in order to produce a suitable negative, I place
in front of the object or in front of the sensitive plate a sheet of transparent glass
of a blue, yellow or red colour according as the object contains much of blue, yellow
or red colour. These coloured glass screens have such an effect upon the coating
of the negative that the print subsequently made therefrom can receive the corre-
sponding tone or colour or is rendered orthochromatic. I obtain in this manner a
negative of a general grey tone from which a paper print from which when properly
treated will allow all the colours to pass or show through which belonged to the
object photographed. The negative is developed and fixed in the usual manner
by means of ferrous oxalate and hyposulphite of soda respectively. When working,
by strong artificial light such for instance as the electric light I project upon the
object, by means of coloured transparent glass, rays of blue, yellow or red light
according as the object contains much of blue, yellow or red. I develop and fix
the negative in the usual manner viz. by means of oxalate of potash sulphate of
iron and bromide of ammonium, and by means of hyposulphite of soda respectively.
The paper or other material well albumenised is for the purpose of my invention
quite immersed in a silver bath of about 15% strength. The paper should be
white and not toned and should be an inch or two larger all round than the
negative. After about five minutes immersion I dry it in the dark and then use it
for printing from the negative. I put the print into a chloride of gold bath of
usual character and leave it in the bath until it assumes a black print or neutral
tone. It is then fixed by hyposulphite of about 10% strength whereupon it is
washed in water for several hours in the usual manner. The print is then put in a
white blotter and while still damp glued on to a wooden frame.
When quite dry by exposure to the air I coat it rapidly on the back with pure
alcohol for the purpose of coagulating the albumen. When the alcohol bas

page_text: evaporated I coat it on the back with a liquid consisting of white venetian
turpentine mixed with pure alcohol or with essence of turpentine; the proportion
being by preference about half of each.
The print is then immediately placed in a suitable stove by preference heated by
means of methylated spirits or by gas and which may suitably be of the form 5
presently to be described. In this stove the print is heated to about 50° C.
According to the difference in the quality of the sensitized paper one, two or three
coats of the solution may be applied with stoving after each coating but these
stovings should be at a less heat than the first stoving that is to say at about 30°
to 40° C. only. For very thin paper one coating is generally sufficient. After 1
about 6 to 12 hours total stoving the paper is dry and very limpid transparent.
The image is now more 'clearly visible on the back than on the front face of the
paper, and it has acquired permanency because the stoving has reduced all the
salts.
Before the colours are applied I give the back of the print a light varnish of 1
isinglass, or by préférence of a saturated solution of gum arabic with one third of
sugar candy added, to form an insulating surface, in order that the colours may not
by penetration to the front alter the transparency of the image. When this
varnish has dried I apply to the parts required on the back of the print, by means
of a brush, a palette knife or a pad, the colours of the object 'photographed. The 2
varying depths of tone in the print modify the effect of the colours seen through
them. I only use oil colours or spirit colours. For retouching if desired I use
colours and dyes dissolved in alcohol; these do not leave a trace of their presence
on the image.
The print is now detached from its wooden frame and may be mounted on Bristol 2
board,' 'on a suitable fabric, or upon a panel or board of some suitable material.
It may then if desired be varnished with a good copal varnish but I prefer that of
Soené's manufacture. The stove may as stated be one heated by spirits or by gas-
and of a square section as shown in the vertical and horizontal sections Figs. 1
and 2 of the drawing, the bottom part A containing the burner ring B and provided 3
with air admission hole C, the middle part D or stove proper provided with racks
or shelves E for placing thereon cross bars Ex, the photographs mounted on"
frames F being placed thereon, and having a door or folding doors D' on the front
side. From the top of the stove proper the walls slope off to the chimney which
has a damper G for regulating the heat and terminates in a short chimney outlet 3
with cap or cowl H to shield it from draughts. The prints are in this construction
as shown entirely exposed to the heat which will travel up in the direction indicated '
by the arrows. I is a thermometer fixed on the inside of the door.
When employing gelatine films I dry the various 'coats in a dry room without'
using stove heat but my invention is not so useful for such films.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that I make no
general claim to a process such as is set forth in my previous Specification No. 16094*
of 1891 but only to the improvements on that process described in the present Specification
and included in the following claim, that is to say what I claim is.
1.
4
4
First The combined process for production of coloured photographs consisting
of the following successive operations viz. the preparation of the negative" for
rendering it orthochromatic, the developing and fixing, the printing therefrom on
paper or other material previously prepared as described, the toning of the print in
the chloride of gold bath in the manner described, the usual fixing and washing of '5
the print, the coating with alcohol on the back for coagulating the albumen, the
coating or coatings with the solution for rendering the print transparent,' the
stoving or air drying operation or operations, the coating with the gum arabic
solution or isinglass solution, and the colouring of the back, with or without the
final retouching, substantially as set forth.

page_text: -
Second. The application in the aforesaid process to the back of the transparent
print of the gum arabio solution described.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.