Improvements in the Manufacture of Photographic Printing Plates.
Year: 1894

page_text: Date of Application, 28th Feb.,
1894
Complete Specification Left. 27th Nov., 1894-Accepted, 23th Feb., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Photographic Printing Plates.
1, AUGUST ZIMMERMANN of 6 and 7 Cross Lane, St. Mary-at-Hill, in the City
of London, Merchant, (a cominunication to me from abroad by The Chemische
Fabrik auf Actien vormals E. Schering of 170 and 171 Müllerstrasse, Berlin in
the Empire of Germany), do hereby declare the nature of this invention to be as
follows:-
My correspondents The Chemische Fabrik auf Actien vormals E. Schering
of 170 & 171 Müllerstrasse Berlin in the Empire of Germany are the inventors
of a process for hardening and tanning glue and gelatinous substances by the
action of formic aldehyde, i.e., formalin so as to make these substances insoluble in
warm water.
Formalin and its sulphite are not however sensitive to the action of light, and
the object of this invention is to obviate this objection.
Gelatine or glue rendered insoluble by the use of formalin and required for
photographic or other purposes, may be exposed to the action of light in com-
bination with a substance giving off oxygen. By this process formic aldehyde will
be converted into formic acid.
For example a plate coated with formalin gelatine, previously treated_with-a
watery solution of a metallic salt such as iron, manganese, silver, copper, and other
metals, preferably their chloride combination, or certain oxidising organic bodies.
capable of developing oxygen under the influence of light, is exposed to light
under a negative or positive.
For instance, when employing chloride of iron, the following chemical change:
The light acting upon the chloride of iron will develop oxygen, as shown in the
above equation, which oxidises the formalin or formic aldehyde into formic acid,
thereby making the insoluble film, soluble in those parts, where the light has been
transmitted.
When washed in warm water the parts made soluble will dissolve, thus giving a
diapositive from a positive and a reproduced negative from a negative.
Formalin when transformed into a sulphurous salt does not act as a hardener..
Gelatine treated with formalin sulphite is therefore soluble, when however this is
saturated with the solution of a substance giving off oxygen, as described in the
first method, and exposed to the action of light, the sulphurous acid will be
oxidised, the formalin thereby liberated and will then exercise its tauning and
hardening properties on the gelatine.
By this process the parts exposed to the action of the light will be rendered
insoluble being in opposition to the result of the first process.
Plates treated in this way will be applicable in the same manner as those made
by the chromic gelatine process, for pigment, stone and metal printing, but with
the advantage that the gelatine, after washing is perfectly colourless.
Dated this 28th day of February 1894.

page_text: Improvements in the Manufacture of Photographic Printing Plates..
I, AUGUST ZIMMERMANN, of 6 and 7 Cross Lane, St. Mary-at-Hill, in the City
of London, Merchant, (a communication to me from abroad by The Chemische
Fabrik auf Actien vormals E. Schering of 170 and 171 Müllerstrasse, Berlin in
the Empire of Germany), do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
My correspondents The Chemische Fabrik auf Actien vormals E. Schering
of 170 & 171 Müllerstrasse Berlin in the Empire of Germany are the inventors of
a process for hardening and tanning glue and gelatinous substances by the action
of formic aldehyde i.e. formalin so as to make these substances insoluble in hot
water. This is described in the Specification of the Patent No. 2036 in the
year 1894.
Formalin and its sulphite are not however sensitive to the action of light, and
the object of this invention is to utilise this property.
.Gelatine or glue rendered insoluble as above described by the use of formalin and
required for photographic or other purposes may be exposed to the action of light
in combination with a substance giving off sufficient oxygen to completely convert
the formic aldehyde into formic acid.
For example a plate coated with formalin gelatine previously treated with a
watery solution of a metallic salt such as iron, manganese, silver, copper, uranium,
and other metals preferably their chloride combination, or certain oxidizing non-
organic or organic bodies capable of developing oxygen under the influence of light,
• is exposed to light under a negative or positive.
For instance, when employing chloride of iron the following chemical change
will take place :
The following quantities may be employed:
10 grammes gelatine.
1 c.c. formic aldehyde.
1 gramme chloride of iron.
100 c.c. water.
The light acting upon the chloride of iron will develop oxygen, as shown in the
above equation which oxidises the formalin or formic aldehyde into formic acid.
thereby making the insoluble film soluble in those parts where the light has been
transmitted.
When washed in warm water the parts made soluble will dissolve, thus giving a
diapositive from a positive and a reproduced negative from a negative.
Formalin when transformed into a sulphurous salt does not act as a hardener.
Gelatine treated with formalin sulphite is therefore soluble, when however this is
saturated with the solution of a substance giving off oxygen as described in the
first method and exposed to the action of light the sulphurous acid will be oxidized,
the formalin thereby liberated and will then exercise its tanning and hardening
properties on the gelatine.
The plate is then washed in warm water the soluble parts being dissolved out
as in the previous process. By this process the parts exposed to the action of
the light will be rendered insoluble being in opposition to the result of the first
process.

page_text: Plates treated in this way will be applicable in the same manner as those made
by the chromic gelatine process, for pigment, stone, and metal printing but with
the advantage that the gelatine after washing is perfectly colourless.
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 what I
claim is :-
1. The manufacture of photographic printing plates from gelatine and formic
aldehyde or its sulphite together with a substance giving off oxygen substantially
as described.
2. The manufacture of photographic printing plates substantially as described.
Dated this 24th day of November 1894.
AUG. ZIMMERMANN.