Improvements in the Manufacture and Subsequent Treatment of Sensitive Paper for Copying Drawings,
Year: 1884

page_text: Improvements in the Manufacture and Subsequent Treatment of
Sensitive Paper for Copying Drawings, Documents Written
of
I HENRY JOSEPH SHAWCROSS, at the Office for Patents, 6 Lord Street, Liverpool,
in the county of Lancaster, Bachelor of Engineering, do hereby declare the nature
my
said invention for "IMPROVEMENTS IN THE MANUFACTURE AND SUBSEQUENT
TREATMENT OF SENSITIVE PAPER FOR COPYING DRAWINGS, DOCUMENTS WRITTEN
ON ONE SIDE AND THE LIKE, BY PHOTOGRAPHY," to be as follows:-
This invention has for its object the obtaining of exact copies of line drawings
or photographs on sufficiently translucent paper in black lines, or in some cases
colored lines on a white surface, and consists in spreading on the surface of the
paper two chemical or compositions, one of them very sensitive to light, and both
having before alteration by exposure to light only a strong affinity for each other,
and capable when combined by wetting or otherwise of dyeing or coloring the
paper to a different shade or color preferat ly to black, but which are placed on the
paper in the uncombined state. By exposing such paper, placed under the drawing
to be copied, to light so as to alter the chemical condition of those parts not covered
by the black lines and then wetting it with any liquid, a solvent of one or both of
the chemicals used, those parts unaffected by the light are dyed through a com-
bination of the two chemical substances.
The method I adopt is as follows:-I cover the surface of the paper with a
solution of one of the chemicals, preferably the one sensitive to light, then thoroughly
dry and rub or press in the other chemical in the form of dry powder. Hitherto
numerous processes have been adopted by which the sensitized paper has been
exposed to light and then dipped in a bath of the other chemical, but mine differs
from these in that both chemicals being applied to the paper before exposure,
nothing but damping and washing in a solvent (such as common water) is required
to develop the image, and also I get practically black lines on a white surface. By
damping the paper prior to immersion so as to effect the chemical combination with
as little liquid as possible and then washing, I avoid the blurring and running
together so common in existing processes.
There are many. chemicals, most of them well known, that will act for this
purpose, those I prefer at present are-for the sensitive solution a mixture of

page_text: (a) perchloride of iron with or without ferric sulphate or other ferric salt, (b) tartaric
or citric acid, (c) gelatine, gum, sugar, or other similar organic matter soluble in
water, () chloride of sodium, alum, or other like salt not absolutely necessary but
found beneficial to the process. For the fixing material I use powdered gallic,
tannic, or meconic acid, or powdered material rich in any such acid, in a soluble
and nearly colorless form, such as catechu, or powdered sulphocyanides, or other
chemicals capable of producing colored precipitates with the ferric salts of iron, but
not with the ferrous salts. The usual solvent I apply is water, but when salts.
insoluble in water are used for the purpose of getting special colors or shades, alcohol
or other solvent of such salt may be employed.
For taking out false marks a weak solution of sulphuric or other acid having
more affinity with iron than gallic acid may be used, or a salt of such acid forming
by double decomposition with gallate, tannate, or meconate of iron, colorless and
preferably soluble salts.

page_text: Improvements in the Manufacture and Subsequent Treatment of
Sensitive Paper for Copying Drawings, Documents Written
I, HENRY JOSEPH SHAWCROSs, Office for Patents, 6 Lord Street Liverpool,
Lancashire, Bachelor. of Engineering, do hereby declare the nature of my said
invention for "IMPROVEMENTS IN THE MANUFACTURE AND SUBSEQUENT TREATMENT
OF SENSITIVE PAPER, FOR COPYING DRAWINGS, DOCUMENTS WRITTEN ON ONE SIDE.
"
AND THE LIKE BY PHOTOGRAPHY and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
This invention has for its object the obtaining of exact copies of line drawings
or photographs on sufficiently translucent paper in black lines, or in some cases
colored lines, on a white surface, and consists in spreading on the surface of the
paper two chemicals or compositions, one of them very sensetive to light, and both.
having, before alteration by exposure to light only, a strong affinity for each other,
and capable when combined by wetting or otherwise of dyeing or coloring the
paper to a different shade or color, preferably to black, but which are placed on
the paper in the uncombined state. By exposing such paper placed under the
drawing to be copied to light so as to alter the chemical condition of those parts,
not covered by the black lines, and then wetting it with any liquid, a solvent of
one or both of the chemicals used, those parts unaffected by. the light are dyed
through a combination of the two chemical substances.
The method I adopt is as follows;-I cover the surface of the paper with a
solution of one of the chemicals, preferably the one sensitive to light, thoroughly
dry it, and then rub or. press in the other chemical in the form of dry powder.
Hitherto numerous processes have been adopted by which the sensitized paper has
been exposed to light, and then dipped in a bath of the other chemical, but mine
differs from these in that both chemicals being applied to the paper before exposure,
nothing but damping and washing in a solvent (such as common water) is required
to develop the image, and also I get practically black lines on a white surface.
There are many chemicals, most of them well-known that will act for this
purpose, those I prefer at present are-for the sensitive solution a mixture of
(a) perchloride of iron, with ferric sulphate or other ferric salt, (b) tartaric or citric
acid, (c) gelatine, gum, sugar, or other like carbo-hydrate, or other similar organic
matter soluble in water, (d) chloride of sodium, alum, or other like salt not absolutely
necessary, but found beneficial to the process.
For the developing material, I use powdered gallic or tannic acid, or powdered
material rich in any such acid, in a soluble and nearly colorless form, such as
catechu, or powdered sulphocyanides, or other chemicals capable of producing
colored precipitates with the ferric salts of iron, but not with the ferrous salts.
The usual solvent I apply is water, but when salts insoluble in water are used for
the purpose of getting special colors or shades, alcohol or other solvent of such salt
may be employed.
For taking out false marks a weak solution of oxalic, sulphurio or other acid
having more affinity with iron than gallic acid may be used, or a salt of such acid

page_text: forming by double decomposition with gallate, taunate, or meconate of iron, colorless
and preferably soluble salts.
The actual chemicals and quantities that I have found best in practice for a
solution to produce a deep black on a white ground are as follows.
Gelatine
Ferric sulphate
Sodium chloride
Tartaric acid
Perchloride of iron
Water
-
-1500-grammes.
600
"
940
,,
188
"
1500
"
11 litres.
is.
This solution is spread over the surface of the paper by means of a roller pad, or
other apparatus just as varnish is spread on paper, and it is dried in the dark; it is
then dusted over with finely powdered gallic or tannic acid; and I thoroughly rub
the powder onto the paper till every part of the sensitive surface is contaminated
therewith. The paper is now ready for sale. In using it the tracing must be laid
over the sensitive surface, and exposed to light in a glass exposure frame, such as
that now used in the ordinary ferro prussiate process.
When the exposure has
been sufficient to duly form the image, the paper is taken out and laid on the
surface of the water, in a tray, sensitive face downward, taking care that every
part is wet by the water, then afterwards reversing to wet the back. The water is
then run off, fresh water run in, and the face well sponged. It' is then hung up
before a fire, or in other position to dry.
The above quantities and ingredients are used when a deep glossy black on a
white ground is desired. When however speed is required in working, and a purple
bue in the lines is no objection, dextrin or glucose can be substituted for or used
with the gelatine. If a deep blue be required an acid ferrocyanide of potassium
can be used instead of the gallic acid in whole or in part. If a deep red be desired,
sulphocyanide of potash may take its place-Catechu will give a green-and by
using other well known chemicals almost any shade or color can be obtained-
as black and dark or clear blue are however the colors usually desired, there is no
need enlarging further than to say that the gallic acid or developing material can
if desired be added after exposure instead of before but I prefer it before.
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
1st In the treatment of sensitive paper, such as described, the addition of
powdered tannic or gallic acid rubbed in, either before or after exposure-whereby
the paper can be developed by being placed in an ordinary solvent such as water.
2nd In the manufacture of sensitive paper, adding to the paper either the
sensitive chemical or the developer or both in the form of a dry powder or film,
by which means the image can be developed by simple immersion in a solvent.
3rd In the manufacture of sensitive paper, the use of the sensitive solution
substantially as herein described.
4th The sensitive paper substantially as herein described.
Bated this 3rd day of March 1885.
W
P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
and 323, High Holborn, London,
Patent Agents for the Applicant.