A New or Improved Process for Producing Photographic Pictures having Colours Resembling those of the Objects from which they are Obtained.
Year: 1891

page_text: The decision of the Comptroller-General of the 16th day of June 1892, allowed,
under Section 18 of the Patents, &c. Act, 1883, an amendment of this
Specification.
Date of Application, 22nd Sept., 1891-Accepted, 24th Oct., 1891
COMPLETE SPECIFICATION (AMENDED).
A New or Improved Process for Producing Photographic Pictures
having Colours Resembling those of the Objects from which they
are Obtained.
I, VICTOR MATHIEU, of 155, Fenchurch Street, London, in the County of
Middlesex, do hereby declare the nature of the said invention and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement, that is to say :-
My present invention has for its object a new or improved process, by which
pictures or prints are obtained from properly prepared photographic negatives, such
pictures being coloured so as to resemble the person, landscape, or other object from
which the negative was in the first place obtained.
In order to put my invention in operation, I take in the usual way a photographic
negative of the object, pictures of which are to be reproduced, such negative being
obtained preferably upon a glass or other plate or surface so sensitized as to
be quite or as nearly as possible orthochromatic, that is to say to produce in the
resulting prints, shades of tone corresponding with the different apparent degrees
of light of the object.
After this negative has been "retouched" in the usual well-known way, where
necessary, a print is taken from it, in the ordinary way, upon a suitable paper,
preferably one so prepared that the gradations of shade in the negative are
accurately reproduced in the print. The print is passed through the usual processes
of toning and fixing, the former being carried on until the print assumes a black
colour, as nearly as possible resembling that of a good engraving. It is then
mounted, whilst still wet, upon a frame by which its subsequent treatment is
facilitated, and it is allowed to dry. When thoroughly dry, the back of the print
is treated with alcohol, applied a. sufficient number of times in succession, in
order to coagulate the albumen, and upon it is then poured a mixture of
alcohol and Venice turpentine, the relative proportions of which in the mixture
may be varied more or less, but which preferably consists of equal parts of each.
The print is then subjected to a strong heat in a hot air oven, the air being allowed
access to all parts of it alike.
When dry, another coating of the mixture of alcohol and Venice turpentine is
applied to the print, and it is again dried, and so on in succession until a sufficient
number of coats have been applied, which may vary more or less as may be found
advisable, a greater or less number being used, the print being subjected to the
baking process between after each coat or layer, but at a somewhat diminished
temperature, until when dry the print is found to be crisp and absolutely transparent,
but without any tendency to crack or break.
It is then preferably coated with a varnish of isinglass, upon which the colours
are then applied.
For this purpose oil colours of suitable character and consistency are used,
applied in the ordinary way with a brush, and it is not found necessary for the

page_text: cheaper class of work to follow with the colours the exact details or outlines of the
different coloured parts, as it is sufficient if the colours are confined roughly within
the required limits.
It is not necessary to use a large number of shades of colour, unless in pictures
of a complicated nature and of a very great variety of shades, the varying depths
of tone in the photographic print themselves modifying the effect of the colours
seen through them. Thus, for example, the same colour-vermilion for instance-
would be available to reproduce the brilliant colour of a flower, and the
subdued tone of a dark red curtain, its brightness being modified in the latter
case by the density and character of the photographic picture through which it
is seen.
Whilst therefore the effect produced by the colours is perfect, the process of
applying them is very simple and cheap and requires little or no skilled or artistic
labour.
After the colours have been applied as described, the print may be retouched if
required in the usual way, upon its face, preferably with alcoholic solutions of dyes
or colours, and after a further application of heat, by which the permanency
drying of the colours is ensured, it can be mounted in any suitable way and may, if
necessary, be protected by one or more coats of any suitable varnish.
I do not confine myself to the precise details of the process, which may be varied
more or less according to the circumstances and conditions in which it is used. For
instance the proportions of the materials forming the coating by which the prints
are rendered transparent as described, as well as the number of times that they are
coated, may be varied more or less, and the temperature at which the prints are
dried as described may also be varied, nor do I claim generally the application of
colours to the back of a more or less transparent photographic print, but
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 process for producing coloured photographic pictures, consisting in first
treating with alcohol photographic prints prepared as described, then applying to
their back a sufficient number of coats of a mixture of alcohol and Venice
turpentine, the prints being baked in a stove between after each such application,
and when dry applying oil colours at the back, and subsequently drying them,
all substantially as described.
2. In the preparation of coloured photographic pictures, the method of baking such
pictures in a suitable oven, after each application of the mixture by which they are
rendered transparent, substantially as described.
3. In the preparation of coloured photographic pictures, the application to the
prints rendered transparent as described of a coat of isinglass varnish at the back, to
receive the colours, substantially as described.
ca
100%
EDWARDS & Co.,
35, Southampton Buildings, Chancery Lane, London,
Agents for the Applicant.