Means for Enlarging Photographic Gelatine Films by the Aid of Chemical Means and Without the Aid of an Enlarging Apparatus.
Year: 1891

page_text: Date of Application, 23rd Sept., 1891
Complete Specification Left, 20th Nov., 1891-Accepted, 19th Dec., 1891
PROVISIONAL SPECIFICATION.
Means for Enlarging Photographic Gelatine Films by the Aid
of Chemical Means and Without the Aid of an Enlarging
Apparatus.
I, ALBERT JOHN EVES HILL 4 Clifton Villas, Clifton Road Norbiton, in the
County of Surrey Art Decorator, do hereby declare the nature of this invention to
be as follows:-
COMPLETE SPECIFICATION.
Means for Enlarging Photographic Gelatine Films by the Aid
of Chemical Means and without the Aid of an Enlarging
Apparatus.
I, ALBERT JOHN EVES HILL of 4 Clifton Villas, Clifton Road, Norbiton in the
County of Surrey, Art Decorator, 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 my invention is to provide means whereby photographic gelatine
films can be enlarged without the use of enlarging apparatus. I effect this by
subjecting the film to the action of a solution in water of citric acid (or other acid
of the like nature) glacial-acetic acid hydrofluoric acid and glycerine."
I assume the film to be operated upon to be mounted upon glass as is customary.
After the photographic picture has been taken developed and fixed it should be
well washed to cleanse it from the developing and fixing agents employed.
If ammonia has been used in developing, it is advisable to neutralize it, and this
may be effected by immersing the film in a bath of acetate of soda (of say one
drachm to each ounce of water) for a time in accordance with the thickness of the
gelatine film. If however the developer has been a fixed alkali in combination
with such agents as pyrogallol hydro-quinone, eikonogen or ferrous oxalate this
treatment with a neutralizing agent is not needed.
The plate or support carrying the film is then (after draining, if the neutralizing
solution has been used) immersed in the enlarging solution and after a time the film
will separate from the plate or support. It is then carefully transferred to water
which may best be done by lifting it out of the solution upon the plate or support
which it has just left and introducing the plate and film into a shallow dish or tray

page_text: containing water. It should be allowed, to, remain for a time in this water bath.
Usually about fifteen minutes will be sufficient.
The final support of the required size for the enlarged, film is then introduced
under the film and, the film is lifted out of the water supported upon this final
support which may be opal glass, paper, canvas, leather or any other suitable
material. The film should then be blown upon, to remove liquid and air from
between the film and support and the support and film should then be placed on a
level surface and be allowed to dry slowly at not too high a temperature the
ordinary temperature of the air usually answering best. Should the enlargement
not be sufficient the film may after drying be again subjected' to the treatment
described.
When the film has been dried and say after about 24 hours. it should be washed
in water and can then be treated as an ordinary film by being for instance retouched,.
intensified or toned.
The proportions of ingredients for the enlarging bath which I have found to
answer best in practice are :-
Hydro-fluoric acid
Citric acid
-
.
Glacial acetic acid
Glycerine
Water
-
-
1 part by weight
4
,,
"
1
"
"
1₁
99+
99-
->
32
"
"
Other vegetable acids of the same nature as citric acid may be used' such as
oxalic acid, tartaric acid and the like but I prefer citric acid:
The hydro-fluoric acid acts as a detacher for the film whilst the citric acid. and
the glacial acetic acid are the active enlarging agents. I use the two together
because glacial acetic acid alone is apt to give objectionable curling or waving of
the film whilst citric acid is not strong enough alone to give such a considerable
enlargement as is usually desirable. The glycerine is used simply as a vehicle
and preservative. Methylated spirit or other preservative usually employed in
photography would therefore be an equivalent for the glycerine in the solution..
To prevent the acids from attacking the silver in the. film so,as; to, cause loss of
intensity in the picture I may add to the solution a sulphate of iron or copper or
both. I prefer to, use, in, the solution with the hereinbefore given, proportions
4. parts by weight of sulphate of iron and th, part by, weight of sulphate of
copper.
The proportions of the ingredients may be varied from those hereinbefore given
it being preferred to make the solution somewhat weaker when the operations are
to be carried on. in a higher temperature than ordinary and stronger when the
temperature is lower.
Although for simplicity I prefer to include the hydrofluoric acid in, the bath
with the enlarging agents yet the film may be first put into a solution of hydro-
fluoric acid and then without washing be subjected to the action of the citric acid
and glacial acetic acid solution.
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, 1,
claim is:
1. For enlarging photographic gelatine films the use of hydrofluoric acid, citric
acid (or acid of a like nature) and glacial'acetic acid substantially as hereinbeföre
described.
2. A bath for enlarging photographic films the said bath being composed of
hydrofluoric acid, citric acid or acid of a like nature, glacial, acetic acid, glycerine
(or equivalent vehicle or preservative) and water with or without the addition of
an agent for preventing loss of density substantially as hereinbefore described:
3. A. solution for enlarging photographic gelatine films the said solution being

page_text: composed of hydrofluoric acid, citric acid, or acid. of a like nature, glacial acetic
acid glycerine and water in or about the proportions hereinbefore stated with or
without the ingredients for preventing loss of density.
Dated this 20th day of November 1891.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.