Year: 1887

page_text: I, EUGEN ALBERT, Doctor of Philosophy, of Munich 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:-
This invention relates to the preparation or making of etched platos for use in
printing and consists in an improved process for deriving on the plate a protecting
layer or surface in the required position by photographic means, thereby preparing
the plate for treatment by acid or etching material.
Heretofore,resinous bodies have been used for this purpose, particularly asphaltum
which possesses the property of being rendered insoluble by light, in turpentine or
usual solvent. This process is however only applicable in certain times, since the
asphaltum is only changed by comparatively long exposure to sunlight or to brilliant
electric light; moreover it necessitates inverted negatives and consequently greater.
trouble and expense owing to the preparation of these.
The improved process consists in the employment of Chrome-gelatine or gelatine
which has been prepared with bichromate of potash or other salt giving to the
gelatine the property of being rendered insoluble by light, powdered asphaltum or
other resinous body being added to the gelatine in a manner somewhat similar to
known processes in which pigment is mixed with the gelatine.
The gelatine is prepared and transferred to the plate in a manner similar to the
process employed in carbon or autotype printing or such process, that is to say the
gelatine is sensitized, dried at 20° C. or thereabouts, exposed to light under a negative
transferred to the metal to be etched and washed in warm water whereby the
unexposed portions are washed away.
If the exposure has been correct the gelatine will be completely washed away at
those places which have been covered by the dark film of the negative and the surface
of the metal will be rendered visible.
The plate with the remaining portions of the gelatine film is then subjected to heat
preferably over a gas or spirit lamp, and the resin is melted thereby throughout the
said film and an acid resisting surface is thus obtained or derived on the plate

page_text: covering all the portions corresponding to the transparent portions of the negative,
that is to say to the dark or shadow portions of the object photographed.
In transferring the gelatine film to the surface of the metal plate, that surface of
the film which was in contact with the negative, is brought in contact with the
surface of the metal plate, so that it is not necessary to employ inverted negatives for
photographing onto the gelatine. A further advantage lies in the sharpness of the
lines obtained by this manner of transfer.
The resinous gelatine is much more susceptible to light requiring only about three
minutes exposure to sun light and about forty-five minutes to diffused light.
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. For the preparation of metal plates for etching, gelatine rendered sensitive to
light in combination with powdered resinous matter or substance substantially as
set forth.
2. For the photographic preparation of a resistant film upon metal plates to be
etched the process consisting in the preparation of a resinous sensitive gelatine film,
exposure thereof under a negative, and transfer and washing for deriving the
undissolved portion of said film on the metal; and the heating of said plate for the
purpose set forth.
3. The combination with the gelatine film of substance adapted to be melted
and to serve as a protective layer against the etching of metal; as and for the
purpose set forth.
Doted this 23rd day of November 1887