Improvements in Transparent Photographic Films, and in the Manufacture thereof.
Year: 1899

page_text: Improvements in Transparent Photographic Films, and in the
Manufacture thereof.
We, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham.
Cheshire, Manufacture, and CILARLES FREDERICK SEYMOUR ROTHWELL, of Wor-
sley Mills, Worsley Street, Hulme, Manchester, Lancashire, Chemist, do hereby
declare the nature of this invention to be as follows:-
new
The object of this invention is to provide a or improved transparent
stripping film for photographic purposes, whereby a transparent paper backing
is is combined with a removable or strippable film during manufacture, and
may remain so combined if desired throughout the various stages or operations
of development, fixing, washing, drying and varnishing, and yet may be ré-
moved or separated from each other afterwards or at any desired time.
The term transparent is used to indicate a paper having little or no opacity,
and such as is known in the trade as transparent paper, that is paper which has
been specially treated after manufacture with the object of making it trans-
parent.
We are well aware that transparent paper has been used before as a support
for films, but in such cases it has always remained a permanent part of the com-
bined film, and in all prints or pictures made from negatives on such films the
grain of the paper has been more or less visible in the print.
We are also well aware that many stripping films have been used, but in
every case the film has been prepared or built upon a backing of strong, thick,
white, and comparatively opaque paper, which, on account of its opacity, ren-
dered it very difficult for the operator to judge the density of the negative or
picture, when developing, by the feeble red light of the dark room.
Our invention therefore consists of a new combination of well known parts,
whereby, a totally new and improved result is obtained and a film produced
which is a great practical advance upon any hitherto known, as it combines all
the advantages of a stripping film, with the additional one of enabling the
operator to judge the density of the negative as easily as with a transparent
glass plate or celluloid film.
The paner backing can be prepared by taking very thin paper and treating it
by any suitable method for rendering it transparent. For rendering ordinary
paper transparent after manufacture there are several methods well known.
For instance it may be soaked in or passed through trough's containing boiled
oil, or castor oil, or a varnish composed of gum dammar, elemi, and the like
in benzole. After removal of the excess the paper is dried, and then passed
through a weak solution of gelatine, and again dried, in order to fix or seal the
transparent medium in the paper. It is afterwards well rolled and glazed
before use.
Another way is to take thin paper and render it more transparent
by repeated calendering or rolling after manufacture, without other treatment,
which result is facilitated if the paper has only been slightly sized.
The next process consists in preparing the paper with a suitable coating or
coatings to enable the film to be readily stripped therefrom.

page_text: A point of the utmost importance is that the film should adhere perfectly to
the paper backing during all the operations until finally dried, and that it
should then, or at any time afterwards be instantly and easily removable.
The material we prefer to use for treating the paper with is flexoid, which we
have found to be better than anything hitherto known for the purpose.
This product has already been made the subject of an application for a patent
in our joint names, dated February 25th, 1899 and numbered 4237, and con-
sists of a compound prepared by treating or dissolving the zinc or aluminium
salts of fatty or resin acids (or a mixture of these salts) with a suitable volatile
solvent such as benzole, coaltar-naptha, benzoline, or other similar light hydro-
carbon, and drying or solidifying the same in the presence of heated air.
The flexoid-treated paper is then rolled or calendered, by mean's of a suitable
calender, until its surface is perfectly smooth and free from grain. The object
of the smooth surface is to leave the film, upon removal from the paper, with
the highest possible degree of transparency and freedom from grain. If, however,
a translucent instead of transparent film is desired, the rolling is omitted, where-
upon the grained surface of the flexoid-treated paper is reproduced upon the
film.
A film formed upon such a prepared backing can be removed therefrom with
the greatest case by simply pulling the film and paper apart with the fingers, no
heat nor solvents being necessary. Moreover, the film never comes off without
being pulled, and never fails to come off when desired.
We do not however confine ourselves to flexoid-treated paper only, as there
are other ways of making the film to strip. For instance, the paper may be
coated with rubber solution, or rubber and collodion, or with a solution of shellac
or hard resinous varnish, from which the film may be removed by pulling. Or
we may coat the paper with a cement soluble in other solvents, or with gelatine
soluble in hot water; in each case of course the film could only be removed
upon treatment with proper solvent.
The film itself is built up on the paper base by coating same with gelatine, or
with any other suitable transparent substances which will be sufficiently strong,
and is finally coated with the sensitive gelatine emulsion, which completes the
process of manufacture.
A film prepared as described has the following advantages over those hitherto
known: It is thin, light, and strong; it is sufficiently transparent to enable
density to be easily and correctly judged in the dark room; it does not cockle
before, during, or after development, and can be dried flat; the film itself can
be easily and with certainty stripped from the temporary paper backing, or can
remain on and the whole used to make prints from.
Films can be manufactured in the way described for various purposes, in-
cluding rapid or slow gelatino-bromide emulsions for development, gelatino-
chloride emulsions for printing out or for development, and others also for nega-
tives, cinematograph positives, lantern or window transparencies, and other
purposes.
Datad
1
ຕາ 1.
P
1000
Improvements in Transparent Photographic Films, and in the
Manufacture thereof.
We, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham,
in the County of Chester, Manufacturer, and CHARLES FREDERICK SEYMOUR

page_text: ROTHWELL, of Worsley Mills, Worsley Street, Hulme, Manchester, in the County
of Lancaster, Chemist, 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:-
The object of this invention is to provide a new or improved transparent film
for photographic purposes whereby a transparent paper base is combined with a
removable or strippable film during manufacture and may remain so combined
if desired throughout the various stages or operations of development fixing
washing drying and varnishing and yet may be removed or separated from each
other afterwards or at any desired time.
We are well aware that photographic films have been made with transparent
paper as a base but in every such instance it has been unremovable and remains
a permanent part of such film but it is very objectionable as on all prints or
pictures obtained from negatives on such films the grain of the paper has been
reproduced and been more or less visible in the print and the presence of the
paper in the finished film has also increased the time necessary to obtain prints
from such negatives.
We are also well aware that many stripping film's have been used but in every
case the film has been prepared or built upon a backing of strong thick white
and comparatively opaque paper which on account of its opacity rendered it
very difficult for the operator to judge the density of the negative or picture
when developing by the feeble red light of the dark room.
Our invention consists essentially in constructing or building up a stripping
film upon a transparent paper base whereby a perfectly new and improved tech-
nical result is obtained and a photographic film produced which is a great
practical advance upon any hitherto known as it combines all the advantages of
a stripping film with the additional one of enabling the operator to judge the
density of the negative almost as easily as with a transparent glass plate or
celluloid film.
In carrying out the invention we take a transparent paper produced or pre-
pared in any of the ways now well known in the art such as by treating paper
with oil varnish gum or other like substances.
The paper is then rolled and glazed before use. The transparent paper form-
ing the base of the film is next coated with a stripping medium or substance
which will render the film formed of gelatine and sensitive emulsion capable
of being stripped or removed after the picture has been obtained thereon.
The stripping medium may be one of the following or other suitable sub-
stances.
(a) A compound or substance prepared by dissolving the aluminium or zine
salts of fatty or resin acids (or a mixture of these salts) with a light hydro-
carbon solvent such as benzol coal-tar naptha or benzoline and then solidifying
by drying.
(b) Rubber solution.
(c) Solution of rubber and followed by collodion.
(d) Solution of shellac or hard resinous varnish.
(e) A cement soluble in water or other solvents such as soluble gelatine.
We prefer to employ the first named substance as the stripping medium as
this we find gives much the best technical results. A point of great importance
is that the sensitive film should adhere to the transparent paper base during all
the operations until finally dried and that it should then or at any subsequent time
be easily removable and this we fully attain by the use as a stripping medium
of the substance prepared by dissolving the aluminium or zinc salts of a fatty
or resin acid then solidifying the same. We prefer to use the aluminium salts
of palmitic oleic stearic or resin acid.
The transparent paper for the base when coated or treated with this material
is preferably rolled or calendered until the surface is perfectly smooth and free
from grain.

page_text: The object of the smooth surface is to leave the film on removal from the
transparent paper base with the highest possible degree of transparency and free-
dom from grain markings. If however a translucent instead of a perfectly
transparent film is desired the rolling may be omitted whereupon the grained.
surface of the transparent paper is reproduced upon the film.
The film itself is built up on the transparent paper base on top of the stripping
medium by coating the same with insoluble gelatine celluloid or similar sub-
stances and finally coating the same with the sensitive emulsion to the required
degree.
A film formed upon such a prepared transparent paper base can be removed
therefrom with the greatest ease by simply pulling the film and paper apart
with the fingers no heat nor solvents being necessary. Moreover the film never
comes off without being pulled and never fails to come off when desired.
A film prepared as described has the following advantages over those hitherto
known. It is thin light and strong; it is sufficiently transparent to enable
density to be easily and correctly judged in the dark room; it does not cockle
before during or after development and can be dried flat; the film itself can be
easily and with certainty stripped from the temporary backing.
Transparent paper films manufactured in the way described may be employed
for various purposes such as for rapid or slow gelatino-bromide emulsion for
development; gelatino-chloride emulsion for printing out or for development;
also for negatives, cinematograph positives, lantern or window transparencies,
and other purposes.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that
what we claim is:-
1. A photographic stripping film in which the stripping medium, and the
film of sensitive emulsion are coated or mounted upon a transparent paper base
substantially as described.
2. A photographic stripping film comprising in its construction a transparent
paper base, a layer or coating of a stripping medium, and a layer or layers of
sensitive emulsion with or without gelatine celluloid or other transparent sub-
stance to strengthen the film substantially as described.
3. A photographic stripping film comprising in its construction a base of
transparent paper, a stripping medium prepared from an aluminium or zinc salt
of fatty or resin acids or mixture thereof dissolved and dried, and a layer or
layers of sensitive emulsion with or without a strengthening of gelatine celluloid
or like substance substantially as described.
4. A photographic stripping film prepared substantially as described.
T
P T
1000
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.