AN IMPROVED. PROCESS FOR MANUFACTURING COLOR SENSITIVE (ISOCHROMATIC OR ORTHOCHROMATIC) PHOTOGRAPHIC EMULSIONS OR PLATES BY DYEING THE SAME WITH DYES HIGHLY SENSITIVE TO LIGHT
Year: 1886

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I HERMANN WILHELM VOGEL of No 124 Kurfürsten Strasse, in the City of
Berlin, Prussia, Germany, Chemist, do hereby declare the nature of my Invention
for "AN IMPROVED. PROCESS FOR MANUFACTURING COLOR SENSITIVE (ISOCHROMATIC
OR ORTHOCHROMATIC) PHOTOGRAPHIC EMULSIONS OR PLATES BY DYEING THE SAME
WITH DYES HIGHLY SENSITIVE TO LIGHT" 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 an improved process for manufacturing color sensitive
isochromatic or orthochromatic photographic emulsions or plates by dyeing the
same with dyes highly sensitive to light.
-
In the year 1873 I discovered that the sensitiveness of the haloid salts of silver
for green, yellow and red rays of light which is very feeble can be augmented by
the addition of bodies which absorb such said rays.
As such bodies I recognized at first Coralline, picrate of methyl rosaniline,
cyanine, fuchsine or aniline red, napthaline red, aldehyde green, metbyl violet
etcetera.
These researches were continued by Waterhouse, Becquerel, Ducos du Nauron,
Eder, Schumann and others and in this manner a large number of such light
absorbing bodies were discovered which I denominate optical sensitizers.
This discovery is the basis of the isochromatic or orthochromatic process now in
use the first isochromatic i.e. color sensitive collodion process was published by
me in the May 1884 number of the "Photographische Mittheilungen" Berlin...
Continuing my researches and experiments I observed that some dyes which
absorb colored rays are not sensitizers for such rays and ascertained that only those
dyes are optical sensitizers which are not only powerful absorbents of certain rays
but which are theinselves readily decomposed by light.
The more readily colored bodies fade under the influence of light the better is
the same adapted for rendering silver sensitive to light-When this fact has once

page_text: been established it will be an easy matter to determine whether any new ye or
color is a good medium for increasing the sensitiveness of the haloid salts of silver
it only being necessary to test its sensitiveness under exposure to light and if it
fades readily it is a good medium for rendering such silver salts sensitive.
In order to carry out this test I prefer to prepare paper, gelatine, or collodion
with the dye or color in question and expose the same to the light (preferably
sunlight) under a perforated screen or photographic negative.
In this manner I ascertained that Cyanine is one of the best sensitizers or
mediums for increasing the sensitiveness of the salts of silver employed in photo-
graphy and I furthermore discovered other valuable colors for achieving the same
object.
"I discovered further that all the-red, violet and blue chinoline and pyrodine
dyes, which cannot be employed by dyers on account of their fading so rapidly
when exposed to light, are first class optical sensitizers for photographic plates.
The application of the aforementioned dyes is extremely easy for instance, a), the
dye is either dissolved in alcohol in the proportion of about 1: 1000 alone or mixed
with other colors and then mixed with the prepared emulsion and with or without
an addition of liquor of ammonia or carbonate of ammonia or
b) the dye is dissolved in water alone or mixed with other dyes with or without
adding liquor of ammonia or carbonate of ammonia to the solution.
The quantity of dye to be added to the emulsion varies according to the quality
of the latter and must be determined by an experiment.-An excellent formula for
many emulsions is :-
2 to 4 cubic centimetres of a solution of chinoline red in alcohol. (1 to 500).
5 drops of a solution of cyanine (1 to 500).
100 cubic centimétres water:
1 cubic centimetre liquor of ammonia.
The emulsion plates are dipped or steeped in this solution for one minute and
then dried-On the other hand I have ascertained that the chemical stability of
.certain dyes such for instance as cyanine can be increased to a great extent by
combining the same with certain other dyes so that colors which produce plates
which will keep only a short time can be used to advantage in combination with
other dyes whereby plates of good keeping quality are produced, for instance
cyanine is very much improved by an addition of chinoline red and for the above-
named reason I prefer in many cases to use mixed dyes instead of single dyes.
י
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The method of rendering photographic emulsions and plates sensitive to
colored rays of light by treating the same with a dye or color which readily fades
when exposed to light substantially as described in the foregoing specification.
2. The method of rendering the haloid salts of silver more sensitive to colored
rays of light by treating the photographic emulsions or photographic plates
containing the same with a solution of chinoline dyes in alcohol substantially as
described in the foregoing specification.
3. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays by treating the same with a
solution of chinoline in water substantially as described in the foregoing specifi-
cation.
4. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays, with a solution of colors made
from chinoldine substantially as described in the foregoing specification.
5. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays, with a combination of two or
more dyes or colors which readily fade when exposed to light substantially as
described in the foregoing specification.

page_text: 6. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays, with a solution of one dye and
subsequently with the solution of a second dye for wet or dry plates substantially
as described in the foregoing specification.
7. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays with a solution of colors made
from pyridine substantially as described in the foregoing specification.
8. The method of rendering the haloid salts of silver in photographic emulsions
and photographic plates sensitive to colored rays by treating the same with a
solution of colors made from cbinoldine substantially as described in the foregoing
specification.