IMPROVEMENTS IN THE PRODUCTION OF COLOURED PHOTO- GRAPHS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Gerard Wenzeslaus von Nawrocki at
the Office of the Commissioners of Patents on the 21st April 1877. A communi-
cation from Gustav Schneider, of Berlin, Germany.
GERARD WENZESLAUS VON NAWROCKI, of the Firm of J. Brandt and G. W. von
Nawrocki, Civil Engineers and Patent Agents, of No. 2, Kock Strasse, Berlin, in the
German Empire. " IMPROVEMENTS IN THE PRODUCTION OF COLOURED PHOTO-
GRAPHS." A communication from Gustav Schneider, of Berlin, Germany.
Photographs have heretofore been coloured by the application of colours on the
front side thereof, and as great skill is required for carrying out the operation in a
satisfactory manner, such coloured photographs are consequently expensive, and as
aniline colours are generally used in their preparation they are not of a permanent
character. Some attempts have also been made to render photographs transparent,
and to colour them from the back, but these have failed on account of the materials
used soaking unequally through the paper of the photograph, thus producing a
spotted appearance of the latter.
According to the present Invention coloured photographs are produced by the
following process:-The paper photograph, which is prepared from the negative in
the usual manner, but is brought to a bluish tint in the gold bath, is coated on the
back very evenly with cold starch paste which has previously been pressed through
a linen bag to remove lumps. When the coating is dry the photograph is fixed with
its front side against a glass plate; for this purpose the surface of the glass has
poured over it a lukewarm glue solution, by preference prepared by boiling one part
of transparent gelatine in ten parts of water; the photograph is then carefully laid
on, and any air bubbles between the paper and the glass are removed by rubbing
with the finger, after which the back of the photograph is coated with the same
gelatine solution. After the gelatine has dried and the photograph is thus made to
adhere firmly to the glass, the back of the photograph is washed with a sponge and
warm water until the whole of the coatings of gelatine and starch paste are
removed, and when the photograph has dried it is rendered transparent by applying
to the back in a cold state a mixture of about 75 parts of rape seed oil with 25 parts
of unsalted lard. This mixture is by preference previously well boiled to thoroughly
incorporate the ingredients. After remaining on the photograph from 6 to 8 hours
this coating is carefully rubbed off with blotting paper, and should the photograph

page_text: have a mottled appearance it is again treated with the same composition, after
which being thus rendered perfectly transparent it is coloured by the application to
the back thereof of ordinary oil colours, care being taken not to use these too dark.
The colours are applied in flat tints, only the shading being supplied by the shades of
the photograph itself, and the several tints are worked into each other where
necessary by "scumbling" in the manner usual in oil painting.
The colours may be made to dry more or less rapidly by the use of a siccative oil.
When the colours are so far dried that they feel sticky but do not come off, the
glass is carefully warmed, and the back of the photograph thereon coated with a
mixture of 5 parts of white wax with one part of turpentine oil, which when cold
can be coated with copal varnish.
By the above described means a coloured photograph is produced greatly superior
in appearance to those coloured in the usual manner, as all the original features
of the photograph are preserved and requiring comparatively little skill and time
in its preparation, in addition to which the picture produced is of a perfectly per-
manent character.