Improvements relating to Means for Fixing and Clearing Photographic Pictures or Images.
Year: 1887

page_text: COMPLETE SPECIFICATION.
Improvements relating to Means for Fixing and Clearing Photographic
Pictures or Images.
I, HERBERT BOWYER BERKELEY, of 29 Southampton Row, in the County of
Middlesex, Chemical Manufacturer 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 the production, in an improved manner, of photo-
graphic negatives and positives made through the agency of the haloid salts of silver
in or on paper or on glass or other surfaces which are formed of or have been prepared
with gelatine, albumen or other suitable substance and which after exposure to light
have been treated with an alkaline developer (such as pyro-gallol or hydro-quinone
and an alkaline solution or salt) .and with other organic substances.
The said invention affords the means for obtaining, on such surfaces, photographic
negatives and positives which shall be free from the yellow or brown tinge, stain or
discolouration usually pervading the aforesaid gelatine or other substances after their
treatment with the developing solution or developer, and which shall have images
generally of a grey or neutral colour heretofore completely obtainable only by treat-
ment of the negative or positive subsequently to development with certain acids or
with alum or other substances, which treatment involves loss of time and other
disadvantages.
I effect this result by the use, after the positive or negative has been developed by
pyro-gallol or hydro-quinone (or other like developer with or without an alkali), of an
improved fixing and clearing mixture applied in solution as follows, that is to say :-
The glass-plate, paper or other support or film bearing the image is taken from the
developing solution and, preferably without being washed in water, is placed directly
In this solution it is allowed
in a bath of my improved fixing and clearing solution.
to remain from about three to five minutes after the haloid salt of silver is seen to be
decomposed. It is then washed in water in the customary manner after fixing.
The advantages of my invention mainly arise from the following conditions well
known to photographers, viz. :-When pyrogallol is made alkaline by the addition to
it of an alkaline substance, such as ammonia, the whole being dissolved in water, a

page_text: rapid absorption of oxygen takes place which causes the solution to assume a dark
brown colour and an insoluble brown deposit is formed. Now, when on the one hand
for instance a gelatine negative is developed in such a solution, the brown colour is
imparted to the film. Moreover this discolouration continues or progresses during the
subsequent treatment of the negative. When, on the other hand, a similar gelatine
negative directly after leaving the aforesaid alkaline developer is placed in my
improved fixing and clearing bath, the acidity of the latier arrests further discoloura-
tion of the negative and also prevents any further development of the image. Moreover
there will be a considerable saving of time and work.
.:
My improved fixing and clearing solution, mixture or composition is essentially as
follows, that is to say:-I take one or more of the bi-sulphites or acid-sulphites
of the alkali-metals (among which I include ammonium) or one or more of the
soluble acid-sulphites of the alkaline earths, or the acid-sulphite of magnesium or the
acid-sulphite of aluminium or any of these combined with the corresponding alkali
salts (preferably adding in either case a sulphite of one or more of the alkalies), and
I mix these with one or more of the thiosulphates (commonly called "hyposulphites")
of the alkalies, or one or more of the thiosulphates of calcium, of strontium or of
magnesium, or the same combined with the corresponding alkali salts.
The aforesaid mixture may be prepared by various methods of which I prefer the
following, viz. I add a bi-sulphite and a sulphite to a thiosulphate as aforesaid, these
being either in the solid state or in solution in water.
But solutions having the properties which are essential for my invention may be
made (1) by decomposing part of the sulphite in solution by an acid or by an
"acid-
salt" (as for example a bi-sulphate) and then adding to, or mixing with the
thiosulphate. (2) Or by the decomposition of a part of the thiosulphate in solution in
water by an acid or by an acid-salt this latter method is preferably followed by
the removal of the sulphur due to the decomposition of a part of the thiosulphate.
(3) Or by the decomposition as above of the whole of the thiosulphate in solution
with the subsequent addition of more of the same or another thiosulphate the object
is in all cases to introduce into the solution of thiosulphate, by decomposition of a
part of it or otherwise or of a sulphite, one or more of the bi-sulphites or acid-
sulphites."
The following equations will illustrate the foregoing explanation.
(1st) SO, Na, + SO, H₂ (sulphite of sodium
sulphite of sodium).
-
sulphurous acid) = 2 SO, H Na (bi-
(2nd) S, O, Na, + SO, H, (thiosulphate of sodium + sulphurous acid) = 2 SO, H
Na+S (bi-sulphite of sodium + sulphur).
(3rd) 2S, O Na, + SO, H. (thiosulphate of sodium + sulphuric acid) = SO₁ Na₂+
S, +2 SO, H Na (sulphate of sodium + sulphur + bisulphite of sodium).
(4th) S, O, Na+ SO, H Na (thiosulphate of sodium + bi-sulphate of sodium) =
SO, Na,+S+ $0, H Na (sulphate of soda + sulphur + bi-sulphite of soda).
I consider the "acid sulphite" or bi-sulphite and the sulphite of an alkali with the
thiosulphate of an alkali to be the best for my purpose, and I generally use those of
sodium or of potassium.
The salts I prefer to use are the sulphite of sodium (SO, Na,) and bi-sulphite of
sodium (SO, Na H), with the thiosulphate of sodium (S, O, Na,). Sometimes I substitute
the sulphite and bi-sulphite and thio-sulphate of potassium for those of sodium, and
in this case there is no necessity to alter the proportions.
The relative proportion in which the salts are used in the mixture may generally be
varied within reasonable limits. But when the mixture is required to work brightly
and clearly after the immersion in it of several films one after the other and at
considerable intervals of time, I find the following proportions will serve my purpose
well, viz. :-
:-
Ten parts by weight of the mixed sulphite and bi-sulphite (about half of which
mixture is preferably bi-sulphite) of sodium or of potassium or of both of these bases
are added to ninety parts by weight of the thiosulphate of sodium or of potassium or
て

page_text: of both of these mixed together, and of the mixed salts I generally use about
100 grains dissolved in one fluid ounce of water.
Instead of preparing my improved mixture as a solution, I sometimes prepare or
mix the constituents in the above described proportions in a dry or semi-dry
condition, in which condition the mixture may be preserved until required for use.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, 1 wish it under-
stood that I claim :-
The improved solution, mixture or composition consisting essentially of a soluble
bi-sulphite or acid-sulphite or soluble bi-sulphites or acid-sulphites of the alkalies or
of the alkaline-earths or of magnesium or of aluminium, and a soluble thiosulphate
or soluble thiosulphates of the alkalies or of the alkaline-earths or of magnesium, as
above set forth.
Dated this 02-1 ...
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.