Improvements in and connected with the Production of Photographic Positives.
Year: 1899

page_text: Date of Application, 14th Jan., 1899
Complete Specification Left, 14th Oct., 1899-Accepted, 2nd Dee., 1899
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Production of Photographic
Positives.
We, Jonx EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, Cheshire,
Manufacturer, and CHARLES FREDERICK SEYMOUR ROTHWELL, of Worsley Mills,
Worsley Street, Hulme, Manchester, Chemist, do hereby declare the nature of
this invention to be as follows:-
Hitherto photographic pictures have been obtained by first making a negative
upon a suitable flexible or rigid support, such as paper, celluloid, or glass, then
developing, fixing, washing, and drying the negative, and afterwards making a
positive on paper, glass, or other material, which likewise required a number of
operations, such as toning, fixing, and washing, before a finished picture was
obtained. Moreover it was necessary to give sufficient exposure to enable printing
density to be obtained in the negative.
The object of this invention is to enable pictures to be produced in a more direct
and rapid manner and with shorter exposures than is possible by the commonly
used methods.
In carrying out our invention we produce a positive picture direct by develop-
ing, fixing, and washing the sensitized surface that has been exposed in the
camera; subsequent processes (such as printing, toning, and washing of a
positive produced from a negative) are therefore not required.
The picture thus obtained may be mounted at once in a frame, or on a card
or other suitable mount. The process is of very great convenience to tourists
and travellers as they may see the finished pictures before leaving the scene of
operations if necessary.
Owing to the fact that such a positive image is required only upon the surface,
and also very much weaker by transmitted light than a negative image such as is
required for printing in the ordinary way, a very much shorter exposure is neces-
sary in order to produce a perfect picture by our process than by any of the usual
methods; in fact, half the usual exposure is sometimes sufficient. This is of very
great advantage to photographers, as it often occurs that sufficient exposure to
produce negatives of the requisite printing density cannot be got under some
conditions of light and subject, and with the existing rapidity of lenses and speed
of gelatino bromide emulsions in the present state of knowledge of the art it is
not possible to improve or alter those factors which govern rapidity beyond a well
defined limit. Therefore, a process that enables results to be got with something
like half the exposure at present required means that, under certain adverse
conditions, good results will often be obtained thereby, where no results of value
at all would be obtained by the present used processes.
The essence of our invention consists in using a sensitized material consisting
of a gelatino bromide emulsion of sufficient rapidity and transparency, coated
upon an opaque flexible backing (for instance black paper), which is first exposed
in the camera, then developed, and fixed, afterwards treated with a whitening
solution, and finally washed and dried. The object of the opaque base is to form

page_text: by its colour, the dark portions of the pictures, the shades and lighter parts being
formed by the varying layers of light coloured deposit which form the image.
The sensitive coating we find may be very thin, much thinner than is usual when
used in the ordinary process, as the images in our process do not require to be of
such an intense nature when developed, as they are further reinforced during the
process of bleaching. For the same reason a much less exposure may be given in
the camera than usual. The sensitive emulsion may be rendered insoluble in
preparation in any well-known way, so that the picture may be dried by heat
if desired.
Although mention has been made of an opaque black backing, that is only
given as an example, for any other preferred colour may be adopted (for instance
a warm brown, a purple, or a sea green), each give pleasing tones to the whole
picture.
A positive picture produced as described is reversed as regards the original
subject, which, in many cases, is no disadvantage, but when it is desired that the
picture shall be viewed as non-reversed we use a reversing prism or a mirror, in
conjunction with the camera lens, to correct this objection, and thereby produce
an exact copy of the original.
Before describing in detail the manufacture of the sensitized material we will
describe the process of working by the photographer in making the pictures.
After exposure in the camera the picture is developed by means of any of the
ordinary photographic developers, preference being given to those which have
little or no staining action upon the film, as for example, hydroquinone, glycin,
or metol. After developing the picture until all the image is clearly
seen, and of sufficient density or strength, it is fixed (that is to SOV,
the unused silver salts are removed), by placing the picture in a solution
of hypo-sulphite of soda of a suitable strength. We find in practice a 10%
to 20% solution acts well, but it may be stronger or weaker than this. Any
other suitable fixer, such as cyanide of potassium for instance, may be used. The
fixing solution is afterwards removed from the film by washing in the usual way.
The film carrying the picture (which is now only just visible), is immersed
in a solution composed of mercuric bichloride, with or without the addition of
ammonium chloride, salt, hydrochloric acid, sulphuric acid, or potassium bromide,
until the picture is whitened sufficiently. We thus obtain a picture composed
of a light deposit, on a ground varying in colour according to the colour of the
base used.
Instead of using mercuric bichloride, we may attain the same end by the use of
bromide of copper, cupric chloride, ferric chloride, or any other chemical which,
when acting upon the silver image, converts it into a white or light coloured
condition. After whitening, the picture is finally washed and then dried, which
latter operation may be assisted by heat if quick drying is required.
In the preparation of the sensitized material it is possible to vary the process
of manufacture according to the exact requirements of the user, without depart-
ing from the principle of the invention.
For instance in the simplest form it is sufficient to coat the sensitive gelatino
bromide emulsion direct upon the opaque paper. In other cases we may use a
white or other non-opaque paper, and coat it with a suitable opaque substratum
before applying the sensitive gelatino bromide emulsion; such a suitable sub-
stratum is celluloid, gelatine, or other like substance, with which is incorporated
a pigment that will render the substratum opaque and of suitable colour.
advantage of this latter method is that any suitable kind of surface may be given
to the paper as a support for the sensitized emulsion.
An
For instance, the surface can be made so hard that the image, when developed,
will not partially "sink" into the pores of the paper; the surface may be very
glossy, bright, and smooth, giving the picture similar characteristics; or it may
have a grain which will give the picture a matt or dead appearance. It is often
desirable to calender the prepared backing before coating with emulsion.

page_text: In any case it is important that the sensitive coating shall be completely
isolated from the opaque paper backing, in order to prevent the image upon the
exceedingly thin and fine sensitive coating from sinking as aforesaid, which
would otherwise not only give the picture a rough surface, but also a dirty and
indistinct appearance with insufficient contrasts between the high lights and
deepest shadows. Therefore the opaque paper backing must either be sufficiently
waterproof and hard on the surface, or otherwise be rendered so with suitable
resinous or celluloid varnish, before applying the sensitive emulsion. For this
reason we prefer to always apply such a varnish unless we use an opaque backing
such as black celluloid or the like, that already has a sufficiently hard surface.
The following may be taken as examples of the building up of a suitable
film acording to our invention, though other examples might be given.
A. Opaque paper backing.
Sensitized gelatino-bromide layer.
B. Paper backing.
Opaque celluloid or other layer.
Sensitized gelatino-bromide layer.
Films made according to this invention are conveniently supplied in lengths,
wound on spools for roll holders and cameras, and by reason of their opaque
backing can be loaded into such exposure apparatus in daylight without a dark
room.
They may also be made in sheets for use in dark slides, magazines, and similar
apparatus.
We are aware that positive pictures have been made direct in the camera by a
sensitized collodion, on metal previously prepared with a black varnish, but in
the present state of knowledge of the photographic art such a film is too slow for
the requirements of modern instantaneous photography, and cannot be rolled upon
spools, and it is only by combining a gelatino-bromide emulsion with an opaque
flexible backing, and by whitening the image after development, that the neces-
sary requirements of a good, cheap, and instantaneous positive film, which may
be wound on rolls or used in flat cut pieces, are fulfilled. This is what our inven-
tion renders possible and actually accomplishes, and as such it constitutes a new
step or advance in the art of photography.
Dated this 18th day of January 1899.
J. E. THORNTON,
C. F. S. ROTHWELL.
Improvements in and connected with the Production of Photographic
Positives.
I, Joux EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, in the
County of Chester, Manufacturer, and CHARLES FREDERICK SEYMOUR 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:
Hitherto photographic pictures have been obtained by first making a negative
upon a suitable flexible or rigid support such as paper celluloid or glass, then
developing, fixing, washing and drying the negative and afterwards making a
positive on paper glass or other material, which likewise required a number of
operations such as toning, fixing and washing before a finished picture was

page_text: obtained. Moreover it was necessary to give sufficient exposure to enable printing
density to be obtained in the negative.
The object of the invention is to enable finished photographic pictures to be
produced in a more direct and rapid manner and with shorter exposures than is
possible by the commonly known methods and to enable positive pictures to be
produced direct by developing fixing whitening and washing the colloid sensi-
tized surface that has been exposed in the camera thus dispensing with all subse-
quent processes such as printing toning and washing of a positive prepared from
a negative.
A positive picture thus obtained may at once be mounted in a frame or on a
card or other suitable mount. The process will be of great convenience to tourists
travellers and others as they may see the finished picture before leaving the scene
of operations.
Owing to the fact that such a positive image is required only on the surface
of the film and very much weaker for viewing by transmitted light than a nega-
tive image which is required or used for printing a much shorter exposure is
necessary to produce a perfect picture, in fact an exposure of half the duration
necessary for the usual processes has been found sufficient by us. This reducing
or shortening of the exposure is of great advantage to photographers as it often
occurs that sufficient exposure cannot be obtained under some conditions of
light and subject to produce negatives with the existing rapidity of lenses and
speed of gelatino-bromide emulsions. It therefore follows that a process by
which results are obtained with half the exposure hitherto required will often
under adverse conditions render good results where otherwise no results of value
would have been obtainable.
This invention consists essentially in a photographic receiving film or plate
comprising a transparent gelatino bromide emulsion coated on an opaque flexible
backing such as black paper celluloid or other similar material which when
exposed in the camera is developed and fixed and afterwards treated with a
whitening solution. The black or coloured base forms by its colour the dark
portions of the picture the shades and light portions being formed by the varying
layers of white coloured deposit which form the image. The sensitive coating
we find may be very thin, much thinner than is usual in the ordinary process
as by our process the images do not require to be of such an intense nature when
developed as they are further reinforced during the process of whitening the
image. For the same reason a shorter exposure may be given in the camera.
In the preparation of the flexible sensitized film or plate it is possible to vary
the process of manufacture according to the exact requirements of the user with-
out departing from the principle of the invention.
In its simplest form it is sufficient to coat the sensitive gelatino-bromide
emulsion directly upon the black or coloured paper. In other cases we may use
a white or other non-opaque paper, and coat it with a suitably coloured sub-
stratum before applying the sensitive gelatino-bromide emulsion: such a suitable
substratum is celluloid, gelatine, or other like substance with which is incorpor-
ated a pigment of suitable colour. An advantage of this latter method is that
any suitable kind of surface may be given to the paper as a support for the
sensitized emulsion.
The surface of the flexible or paper backing may be so hard that the image
when developed will not partially “sink" into the pores of the paper; the sur-
face may be very glossy, bright and smooth giving the picture similar character-
istics or it may have a grain which will give the picture a matt or dead appear-
ance. It is often desirable to calendar the prepared backing before coating with
emulsion.
In any case it is important that the sensitive coating shall be on the surface
of the black or coloured paper backing only and shall not be allowed to penetrate i
into the pores or substance of the film base in order to prevent the image upon the
exceedingly thin and fine sensitive coating from sinking as aforesaid, which would

page_text: tinct appearance with insufficient contrasts between the high lights and deepest
shadows. Therefore the black or coloured paper backing must either be
sufficiently waterproof and hard on the surface, or otherwise be rendered so
with suitable resinous or other varnish, before applying the sensitive emulsion.
For this reason we prefer always to apply such a varnish unless we use an opaque
backing such as black or coloured celluloid or other flexible material that already
possesses a sufficiently hard or non-absorbent surface.
A suitable positive film may be built up as follows--
A. Black or coloured paper backing or base.
Sensitized gelatino bromide layer.
B. Paper backing or base.
Black or coloured waterproof layer.
Sensitized gelatino bromide layer.
Films made according to this invention are conveniently supplied in lengths,
wound on spools for roll holders and cameras, and by reason of their opaque
backing can be loaded into such exposure apparatus in daylight without a dark
rooni.
They may also be made in sheets for use in dark slides magazines and similar
apparatus.
In use the photographer who produces the picture places the sensitized positive
film in the camera for exposure and after an exposure of very short duration the
picture is developed by means of any of the ordinary photographic developers
preference being given to those which have little or no staining action upon the
film as for example, hydroquinone, glycin or metol. After developing the picture
until all the image is clearly seen and of sufficient density or strength, it is fixed
(that is to say, the unused silver salts are removed), by placing the picture in a
solution of hypo-sulphite of soda of a suitable strength. We find in practice a
10% to 20% solution acts well, but it may be stronger or weaker than this. Any
other suitable fixer, such as cyanide of potassium for instance may be used. The
fixing solution is afterwards removed from the film by washing in the usual way.
The film carrying the picture (which is now only just visible) is immersed in
a solution composed of mercuric bichloride, with or without the addition of
ammonium chloride, salt, hydrochloric acid, sulphuric acid or potassium bromide
until the picture is whitened sufliciently. We thus obtain a picture composed
of a light deposit, on a ground varying in colour according to the colour of the
film base used.
Instead of using mercuric bichloride we may attain the same end by the use
of bromide of copper, cupric chloride, ferric chloride, or any other chemical
which, when acting upon the silver image converts it into a white or light coloured
condition. After whitening the picture is finally washed and then dried which
latter operation may be assisted by heat if quick drving is required.
be
We are aware that positive pictures have been made direct in the camera by a
sensitized collodion, on metal previously prepared with a black varnish, but in
the present state of knowledge of the photographic art such a film is too slow
for the requirements of modern instantaneous photography, and cannot
rolled up on spools, and it is only by combining a gelatino-bromide emulsion
with a black or coloured backing and by whitening the image after development,
that the necessary requirements of a good, cheap and instantaneous positive
film, which may be wound on rolls or used in flat cut pieces are fulfilled. This
is what our invention renders possible and actually acomplishes and as such it
constitutes a new step or advance in the art of photography.
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. In a film for the production of direct positive pictures the combination with

page_text: a black or coloured flexible base comprising paper celluloid or other flexible
material of a layer or coating of gelatino bromide emulsion coated direct thereon
substantially as described.
2. A film for the production of direct positive pictures consisting of a black
or coloured flexible backing or base of paper celluloid or other suitable flexible
material coated or covered with a layer of gelatino bromide emulsion and with
a waterproof isolating material interposed between the flexible backing and the
sensitive layer to prevent the image from sinking substantially as described.
3. A film for the production of direct positive pictures consisting of a flexible
backing or base of paper celluloid or other suitable flexible material a coating
of a black or coloured medium to render the backing opaque and also serve to
isolate the sensitive coating and a layer of a sensitive gelatino-bromide emulsion
substantially as described.
4. The method of producing direct positive pictures consisting in exposing (in
a camera) a flexible film base coated with a gelatino bromide emulsion, develop-
ing and fixing same, and subsequently whitening the image so obtained and then
washing and drying the film substantially as described.
5. In the production of a direct photographic positive picture the use with a
flexible opaque film base coated with a gelatino bromide emulsion of a reversing
prism or mirror in combination with a photographic camera for the purpose of
producing a non-reversed positive picture substantially as described.
6. An opaque flexible film of paper celluloid or other material substantially
as and for the purpose described.
D