Improvements in the Manufacture of Stripping Films for Photographic Purposes.
Year: 1895

page_text: Date of Application, 29th May, 1895
Complete Specification Left, 11th Nov., 1895-Accepted, 14th Dec.,
1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Stripping Films for
Photographic Purposes.
JAMES BOOKER BLAKEMORE WELLINGTON The Elms, Elstree Herts, do
hereby declare the nature of this invention to be as follows:―
This invention relates to the manufacture of flexible transparent films intended
for the support of photographic emulsions, and has for its purpose to provide a film
of insoluble gelatine which is supported during exposure upon a backing of paper,
cardboard or the like from which backing it is stripped prior to the process of
printing,
Hitherto stripping films have been formed by interposing, between an insoluble
gelatine and a paper backing a layer of soluble gelatine which was after develop-
ment and prior to the process of printing, dissolved by means of hot water, thus
releasing the negative from its temporary support. In films of this class the
insoluble gelatine was so thin that it was necessary to transfer it to another
perinanent transparent support, this transference forming a necessary part of the
process. Stripping films of this kind were found to be unsatisfactory in various
respects and the process is now no longer to be met with in practice.
In stripping films manufactured according to my invention the disadvantages
hitherto obtaining are overcome. The stripping is effected without the use of hot
baths or special treatment of any kind and it is not necessary to transfer the stripped
film to any other support.
The
In carrying my invention into effect I coat upon any suitable paper as for
instance upon the well known photographic papers coated with baryta, whether
matt or calendered, a substratum containing a suitable proportion of any gum or
resin dissolved in any of the well known solvents, which are in general use for this
purpose. In practice I bave found that equal parts of gum mastic and gum thus
dissolved in methylated spirit will give satisfactory results; but I am aware that
good results may be obtained with mastic & thus in varying proportions or with
other gums and resins as for instance damar, copal and their congeners.
thickness of the solution of these gums is in like manner, capable of considerable
variation, and will depend in great measure upon the means which are adopted for
coating the paper: for instance if the paper be coated by immersion in a trough,
a solution of 4 parts of gum mastic 4 parts of gum thus and 40 parts of methylated
spirit will be found to answer well. The gum solution may if desired be stained
with some non actinic color in order to prevent the transmission of light through
the film and to diminish halation.
Having thus prepared my paper backing by coating it with a substratum of gum
and permitted it to dry I proceed to coat thereupon the layer of insoluble gelatine
which is destined to form the body of the film itself. This body I form of gelatine,
which render insoluble by the addition thereto, immediately prior to coating,
a suitable proportion of soda alum, chrome alum or any of those well known
chemicals which have the property of rendering gelatine insoluble when dry.
I coat this toughened gelatine upon the gummed paper backing in sufficient
thickness to give me when dried and stripped from the gummed paper, a film of
sufficient substance to serve as the support of a negative. In practice I prefer to
make the gelatine so thick that the resulting film, together with the emulsion

page_text: spread upon it, measures from two thousandths to ten thousandths of an inch in
thickness when dry, in order that it may not be necessary to transfer the film to
another support. If it be desired the paper backing may be coated with the
insoluble gelatine upon both sides, the coating upon the back in such case having
for its purpose to prevent the warping & cockling of the entire support through
changes of temperature & hygrometric conditions. When the toughened gelatine
is dry I coat upon it the sensitive emulsion in the manner well known to those skilled
in the art. This process completes the manufacture of the film.
I expose my improved film while still in contact with the backing of gummed
paper upon which it is formed, this backing giving body and rigidity to the film
which is advantageous. In like manner I preferably effect the process of develop-
ment, fixing & washing upon the paper backing. When the washing is complete
separate or strip the body film of insoluble gelatine together with the emulsion
coating upon it by pulling off the backing of gummed paper, the function of the
gum substratum in which lies the essence of my invention being to facilitate the
stripping process. Having thus separated the negative with its permanent support
I preferably squeegee this upon a ferrotype plate, sheet of talced or waxed glass or
similar plane & polished surface upon which it is permitted to dry & from which it
derives a flat & polished surface. The negative may be squeegeed with either surface
in contact with the polished plate; should it be desired to remove any grain or
matt appearance of the paper backing which may appear upon the insoluble gelatine
body, this side may be placed for this purpose in contact with the polished plate.
When the negative becomes thoroughly dry it is peeled from the polished surface
and is then ready for printing.
Dated this 20th dow of Mov 1905
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Stripping Films for
Photographic Purposes.
I, JAMES BOOKER BLAKEMORE WELLINGTON, of The Elms, Elstree, Herts,
Manufacturer of Photographic Papers, do hereby declare the nature of this inven-
tion, and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
a
This invention relates to the manufacture of flexible transparent films intended
for the support of photographic emulsions, and has for its purpose to provide
film of gelatine which is supported during exposure upon a backing of paper.
cardboard or the like, from which backing it is stripped prior to the process of
printing.
Hitherto stripping films have been formed by interposing between an insoluble
gelatine and a paper backing, a layer of soluble gelatine which was, after develop-
ment and prior to the process of printing, dissolved by means of hot water, thus
releasing the negative from its temporary support. In films of this class the
insoluble gelatine was so thin that it was necessary to transfer it to another
permanent transparent support, this transference forming a necessary part of the
process. Stripping films of this hund were found to be unsatisfactory in various
respects and the process is now Lo longer to be met with in practice.
In stripping films manufactured according to my invention the disadvantages
hitherto obtaining are overcome. The stripping is effected without the use of hot
baths or special treatment of any kind, and it is not necessary to transfer the
stripped film to any other support.
In carrying my invention into effect I coat upon one or both sides of any suitable
paper, as, for instance, upon the well known photographic papers and also those

page_text: coated with baryta, whether matt or calendered, a substratum containing a
suitable proportion of any gum or resin dissolved in any of the well known solvents
which are in general use for this purpose. In practice I have found that good
results may be obtained with mastic and thus in varying proportions or with other
gums and resins, as, for instance, damar, copal, and their congeners, but I prefer to
use gum sandarac or gum copal. The thickness of the solution of these gums is in
like manner capable of considerable variation and will depend in great measure
upon the means which are adopted for coating the paper. For instance, if the
paper be coated by immersion in a trough, a solution of 1 part of gum sandarac or
guin copal and 10 parts of methylated spirit or other solvent will be found to
answer well. The gum solution may, if desired, be stained with some non-actinic
color in order to prevent the transmission of light through the film and to diminish
halation.
Having thus prepared my paper backing by coating it with a substratum of gum,
and permitted it to dry, I proceed to coat thereupon the layer of gelatine which is
destined to form the body of the film itself. This body I form of gelatine, which
I preferably render insoluble by the addition thereto, immediately prior to coating,
of a suitable proportion of soda alum, chrome alum, or any of those well known
chemicals which have the property of rendering gelatine insoluble when dry.
I coat the gelatine upon the guinned paper backing in sufficient thickness to give
me, when dried and stripped from the gummed paper, a film of sufficient substance
to serve as the support of a negative. In practice I prefer to make the gelatine
so thick that the resulting film, together with the emulsion spread upon it, measures
from two thousandths to ten thousandths of an inch in thickness when dry, in order
that it may not be necessary to transfer the film to another support. If it be
desired the paper backing may be coated with the gelatine upon both sides, the
coating upon the back in such case having for its purpose to prevent the warping
and cockling of the entire support through change of temperature and hygrometric
conditions. When the gelatine is dry I coat upon it the sensitive emulsion in the
manner well known to those skilled in the art. This process completes the
manufacture of the film.
If desired the silver salts may be emulsified with the gelatine used to form the
body film, in which case the body film and sensitive surface are produced at one
and the same operation, thus avoiding the loss of time involved in the double
process and the intermediate drying operation.
I expose my improved film while still in contact with the backing of gummed
paper upon which it is formed, this backing giving body and rigidity to the film,
which is advantageous. In like manner I preferably effect the process of
development, fixing and washing upon the paper backing. When the washing is
complete, or at any stage of the process after exposure of the film, I separate or
strip the body film of gelatine, together with the emulsion coating upon it, by
pulling off the backing of gummed paper, the function of the gum substratum, in
which lies the essence of my invention, being to facilitate the stripping process.
Having thus separated the negative with its permanent support, I preferably
squeegee this upon a ferrotype plate, sheet of glass polished by means of French
chalk or tale or with wax, or other similar plane and polished surface, upon which
it is permitted to dry and from which it derives a flat and polished surface.
negative may be squeegeed with either surface in contact with the polished plate;
should it be desired to remove any grain or matt appearance of the paper backing
which may appear upon the gelatine body, this side may be placed for this purpose
in contact with the polished plate. When the negative becomes thoroughly dry it
is peeled from the polished surface and is then ready for printing.
The
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. A stripping film for photographic purposes consisting of the combination of a

page_text: paper backing, a substratum consisting of a solution of a suitable gum or resin
coated thereon, a layer of gelatine upon such substratum, and a final layer of
sensitive emulsion, substantially as herein described.
2. A stripping film for photographic purposes consisting of the combination of a
paper backing, coated on both sides with a solution of a suitable gum or resin,
a layer of gelatine upon one side of such gum or resin coated paper, and a final
layer of sensitive emulsion, substantially as herein described.
3. A stripping film for photographic purposes consisting of the combination of a
paper backing coated with a substratum of gum or resin stained with a non-actinic
color, a layer of gelatine upon such substratum, and a final layer of sensitive
emulsion, substantially as herein described.
4. A stripping film for photographic purposes consisting of the combination of a
paper backing coated with a substratumn of gum or resin, and a layer of sensitive
gelatine of sufficient substance to form the film body in addition to the sensitive
surface, substantially as herein described.
D thi. 11th dov of November 1895.
HARRIS & MILLS,
23 Southampton Buildings, London, W.C., Agents.
HARRIS & MILLS,
23 Southampton Buildings, London, W.C., Agents.