Improvements in Photographic Negatives and Sensitised Plates for Use in Photo-illustrative Processes.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Photographic Negatives and Sensitised Plates for
Use in Photo-illustrative Processes.
We HERBERT DEVERIL, Photo-lithographer and WILLIAM GALLAGHER Gentleman
both of Sydney in the Colony of New South Wales, 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 improvements in photographic unvarnished negatives and
in Photographic sensitised plates by means of which the pictures obtained upon them
may be printed in greasy or fatty ink on the ordinary Laterial and transferred to stone,
metals, wood, glass, porcelain, or other substances for printing, etching or engraving,
or other illustrative or ornamental purposes and revealed thereon in minutest detail and
with half tones and all degree of shadow clearly defined.
This improvement in photographic negatives and sensitised plates for use in photo-
illustrative processes is comprehended in the obtainment in the negative from which
the picture is printed on the usual and ordinary transferring material of non-actinic,
opaque, or semi-opaque dots, lines, grains, or such like. Those dots, lines &c. may
be
of a latent character upon sensitised plates and are developed with the pictures upon
such plates after exposure in the camera, or they may be superinduced upon developed
unvarnished negatives.
"
"
In carrying out this improvement in photographic negatives and sensitised plates for
ase in photo-illustrative processes what is for convenience sake termed a mater is
first prepared. This consists of a sheet of glass or transparent or semi-transparent
paper or other suitable substances rendered opaque or non-actinic except in dots, lines,
grains or such like which remain transparent or semi-transparent. This "mater" may
be prepared in any convenient manner for instance it may be a dry print on thin
photographic paper (preferably Rives) obtained from a lithographic stone evenly
coated with stiff lithographic ink or preferably it is an ordinary photographic negative
of a drawing or material or substance which will give the desired result. Having this
"mater" at hand it is used as desired for converting the "plates" or the " negatives"
into suitable means for obtaining the required transfers."
An ordinary sensitised plate (of Gelatino-Bromide of Silver manufacture) with its
face upwards and its back protected with a dark non-reflecting material is exposed for
a very brief period in an ordinary printing frame under a "mater" (face downwards)
to the action of weak white or actinic light, say, for from three to twenty seconds
according to the density of the "mater" to the light of an ordinary paraffin candle
and it is then ready for use immediately or at any future time to obtain a picture by
exposure in a camera and which after ordinary development will be seen to consist of
a greater or lesser quantity of minute opaque or semi-opaque dots, lines, grains &c. as
are required to produce white dots or grains &c. in the resulting transfer, and it is
printed from upon sensitised transfer paper or material in the ordinary way. Instead
of being treated under the "mater" before exposure in the camera the "plate" may
be so treated after exposure in the camera but before development.
An ordinary unvarnished developed negative (having a gelatine film) is immersed
in a saturated solution of Bi-chromate of Potash for, say ten to fifteen minutes (the
surplus solution blotted off to prevent crystallization of the salt) and then dried in the
dark when it becomes sensitive to white or actinic light. It is then exposed to strong
white light (sun light) in a similar way to the exposure of the "plates" before
described under the mater" until opaque or semi-opaque dots, grains &c. appear, such
dots &c. being in fact minute portions of the negative reduced into a resinous substance
which remaining in union with oxide of Chromium is insoluble in water.
The negative
is then washed and when dry is ready for immediate or any future use in printing a
"transfer."

page_text: We would have it understood that we do not confine ourselves to the precise
manner and the details thereof described of carrying our improvements in photo-
graphic negatives and sensitised plates for use in photo-illustrative processes into
practical effect so long as the nature of the said invention he retained, but,
Having now particularly described and ascertained the nature of our said invention
and in what manner the same is to be performed, we declare that what we claim is :—
First A sensitised photographic plate having upon it latent dots or marks which
during development become and afterwards remain opaque or semi-opaque or non
actinic substantially as herein described and explained.
Second A photographic gelatine negative having upon or within the developed
picture superinduced opaque or semi-opaque or non-actinic dots or marks substantially
as herein described and explained.
66
Third A sensitised photographic plate for the obtainment of negatives for photo-
illustrative processes prepared in the ordinary manner and before or after exposure in
a camera by an exposure to light under a mater or non-actinic sheet having trans-
parent or semi-transparent dots or marks substantially as herein described and
explained.
Fourth A photographic gelatine negative for photo-illustrative processes prepared
by converting minute portions or dots or marks of an ordinary photographic negative
into a substance insoluble in water and preferably by treating such negative with
Bichromate of Potash and exposing it to light under a
"mater or non-actinic sheet
having transparent or semi-transparent dots or marks substantially as herein described
and explained.
Dated this Thirtieth day of April 1880
HERBERT DEVERIL.
W. GALLAGHER.
J. C. Mewburn,
55 & 56, Chancery Lane, London, Patent Agent.