An Improved Method of Making Printing Surfaces by Photographic Means.
Year: 1894

page_text: Date of Application, 10th Feb., 1894
Complete Specification Left, 12th Nov., 1894-Accepted, 9th Feb., 1895'
PROVISIONAL SPECIFICATION.
An Improved Method of Making Printing Surfaces by Photographic
Means.
FRANK STERNBERG Hillside Cottage Bushey Herts do hereby declare the
nature of this invention to be as follows:-
The principle of my invention is that of washing away in different degrees any
suitable substance which is sensitive to light. The substance being first made
either into the form of a texture or that of a film divided by dots or lines.
To make a surface for copper-plate printing a cast is made (in any suitable
substance which is sensitive to light) of a textured plate such as a rocked mezzo-
tint plate or mould of one. After exposing this textured cast to light under a
negative the texture is washed away in different degrees according to the exposure
which it has received.
For making surfaces for typographic printing a plate of any suitable substance
is coated with a film (preferably pigmented) which is sensitive to light, and then
exposed to light under a negative bearing (or simultaneously with) a dividing
grain of opaque dots or lines. Before the washing away is commenced the whole
surface of the film, excepting all those parts which have been protected from the
light by the opaque dots or lines, is covered with any suitable resist which will
prevent the sensitive film from being washed away on the surface. All those parts
of the film which have been protected from the action of the light by the opaque
dots or lines are then washed out and those parts of the film which have been
exposed to light are washed away beneath the resist in different degrees, the
washing away taking place at the edges of the dots or lines.
The resist may consist of a second sensitive film which is insoluble in the solvent
to be used for the underneath film, the dots or lines being washed out in the top
film before the solvent of the underneath film is applied. Before the plate is
coated with any sensitive film it may be painted with a resist to the acid or solvent
to be used for etching it.
If positives bearing opaque dots or lines are used instead of negatives the plates
may be used for copper plate printing.
1 1 dow of ahnuary 1004
An Improved Method of Making Printing Surfaces by Photographic
Means.
I, FRANK STERNBERG of Hillside Cottage, Bushey, Hertfordshire, Artist and
Engraver, 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 invention consists in making printing surfaces by the principle of decreasing
the texture, or areas of divided surfaces of substances capable of being hardened
by light, by washing away the texture in the less hardened parts, or by washing
away the less hardened parts of divided surfaces, under a resist, at the sides of the
dots or lines by which they are divided.

page_text: To make a textured printing surface, I take a cast in any suitable sensitive
substance, such as gelatine and bi-chromate of potash, from any suitable textured
plate having numerous raised points or lines, such as a rocked mezzotint plate or an
electrotype or mould of one. I expose this textured gelatine casting to light under
a negative and then allow it to absorb moisture until its less hardened parts are
swelled up in relief so that I may wash away the top of the texture in the raised
parts by rubbing with a wet rag stretched over a flat surface. When the texture
in the swelled-up parts appears to be rubbed away enough to represent the lighter
parts of the picture, I either make an electrotype facsimile of the textured gelatine
casting in its damp state, by well known method, and finish the electrotype plate
by scraping or grinding away the texture in the raised parts where it had not been
sufficiently rubbed away in the gelatine, or I dry it and print from it in a copper-
plate press after it has been hardened all over by light.
If a positive is used instead of a negative in making such an electrotype plate as
just described it may be used for surface printing.
1 make the textured gelatine or other sensitized casting by drying a sufficiently
thick coating of melted gelatine and bichromate of potash (or other sensitized
substance) upon the textured plate. I strip it off when dry and mount it upon any
suitable flat surface.
To make a divided printing surface, I coat a zinc or other plate with albumen
and bi-chromate of potash or other sensitive substance. After exposing this
sensitive surface to light under a half-tone negative bearing numerous opaque dots,
I thinly coat it with a resist, such as photo-transfer ink, and then allow the
unhardened dots (which have been entirely protected from light by the opaque
dots on the half-tone negative) to absorb moisture until the resist can be easily
wiped off their surfaces; being careful, in doing so, not to wipe any of the resist
off the parts which have been exposed to light. When the resist remaining upon
the exposed parts is dry, or has been sufficiently reinforced to prevent the sensitive
coating from being washed away on its surface, the unhardened dots are entirely
washed out and the less exposed parts under the resist are washed away sideways,
the washing away taking place at the sides of the washed-out dots by which the
sensitive coating is divided. The result is that the area of the sensitive surface
remaining upon the zinc plate between the washed-out dots is decreased most in
those parts which have been protected from light by the densest parts of the half-
tone negative between the opaque dots. Having thus bared the zinc plate in the
washed-out dots of varying sizes, the sensitive coating may be hardened by light or
other well known method, and the zinc plate etched in the usual way.
Positives bearing opaque dots may be used as just described for making divided
surfaces for copper-plate printing. Such half-tone negatives or positives may bear
opaque lines instead of dots; and the opaque dots or lines may be upon a separate
film.
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. In the production of textured printing surfaces, the use of sensitized castings
from textured plates for the purpose of making swelled or washed-out photographic
reliefs.
2. In the production of divided printing surfaces, the means of decreasing the
area of the surface of a sensitive substance, after exposing it to light under a half-
tone negative or positive with opaque dots or lines, by washing away the less
exposed parts sideways, under a resist, after the unexposed dots or lines have been
washed out.
Dated this 10th day of November 1894.