New or Improved Paste for the Prevention of Discolouration of Photographs Mounted upon Bristol-board and the like.
Year: 1892

page_text: Date of Application, 26th Nov., 1892
Complete Specification Left, 17th Aug., 1893-Accepted, 23rd Sept., 1893
PROVISIONAL SPECIFICATION.
A. New or Improved Paste for the Prevention of Discolouration of
Photographs Mounted upon Bristol-board and the like.
We, HERMANN WILHELM VOGEL, of 124 Kurfürsten Strasse, Berlin, Kingdom
of Prussia, Germany, Professor, and JACOB WEINBERG of 50, Wasserthor Strasse,
Berlin, Kingdom of Prussia, Germany, Manufacturer do hereby declare the nature
of this invention to be as follows:-
It is a known fact that photographs mounted on Bristol-board are liable to
become yellow and all attempts to prevent this have up to the present failed.
Experiments we have made as to the nature of this discolouration show that it
can only result from the presence of impurities either in the photographs or in the
Bristol-board. For instance the silver prints are often treated with too small a
quantity of fixing salt, and the fixing is therefore defective, the following insoluble
annound remaining in the pictures:
Na,S,O,+ Ag₂SO₁ + aq = N₁₂S₂O₂ + Ag₂S + SO₂ + aq
(III)
Sulphide of silver is thus formed, producing discolouration of the picture.
Again the fixed pictures are often insufficiently washed out, small quantities of
the salt being left and also producing in time discolouration.
Then again pictures properly prepared and washed out, are often dried on impure"
blotting-paper containing fixing salts or hung on strings containing various impurities,
and in this manner again soiled.
The cardboard used for mounts can also contain impurities, the paper used being
often bleached with chlorine. This, and the reagent used to remove the excess of
chlorine, called antichlorine (Na2S2O3) are according to the following equation:
Na₂SO + 3 H₂O + 6 Cl = 6 HCl + Na₂SO
not of themselves harmful to the paper, but unfortunately a superfluity of hypo-
sulphite of soda is often present, and according to the above formula III causes a
precipitate of sulphur which produces discolouration.
Our invention consists now in overcoming the above defects by using a means for
removing the sulphurous impurities, thus preventing this discolouration.
We attain this object by employing as a glue a paste of starch mixed with iodine
in varying proportions for instance 10 ccm. of a solution containing 1 gr. of iodine
in 10 cem. of alkali are added to 100 ccm. of freshly prepared pure starch paste.
This mixture is thoroughly stirred the paste changing to a dark blue mass which
may be coated on paper or on card-board by means of a brush.
Our improved glue is employed either for uniting the several layers of paper of
which a sheet of card-board is composed, of for mounting paper photographs upon
paper or upon card-board. This glue will prevent the card-board and the photo-
graphs from yellowing. This yellowing, which is a defect occurring frequently
with photographs mounted with ordinary glue or paste is due to chlorides and

page_text: sulphurous or other impure admixtures either contained in the paper or card-board,
or adhering to the photograph in consequence of the previous operations, for
instance owing to defective fixing or insufficient washing of the photograph. Now
iodine is a very efficacious agent for destroying such compounds as are capable of
yellowing the photographs. Hyposulphite of soda is caused to combine with
oxygen and thus to form hyposulphite of soda, as is represented by the equation :
Na₂S +61 +3 H₂O = Na₂SO₂ + 6 HI
Experiments have proved that iodine has no noxious effect upon paper photographs
in which the sensitive part of the paper contains silver salts. The experiments
have also demonstrated the fact that our improved glue is efficacious in preserving
the photographs for any length of time. It has been further ascertained that the
addition of 10 parts of tincture of iodine (1:10) to 100 parts of starch-paste is the
highest proportion which it will necessary to employ when the paper contains as
much as 1 per cent. of impurities. It will be obvious that the amount of iodine
which is to be added will in each case depend on the proportion in which impurities
are admixed in the paper, card-board, or photographs.
It will be obvious that our improved glue may be employed with great advantage
for uniting the several layers composing a sheet of card-board, especially if such
card-board is to be used for mounting photographs thereon.
It sometimes occurs that the paste or glue is squeezed out laterally of the
photograph to be mounted, thereby occasioning blue spots. In this case we take a
small sponge and soak it in a solution of 1 part of chemically pure sulphite of soda
in 1000 parts of water. The sponge is pressed so as to remove the greatest part of
the solution it has soaked, and is passed over the blue spots; the blue colour will
disappear very rapidly, and it will be sufficient to wipe the moisture away with a
clean piece of cloth.
Dated this 26th day of November 1892
HERMANN W. VOGEL,
JACOB WEINBERG,
By Geo. Thos. Hyde,
4, Moorfields, Fore Street, London, E.C., Agent for the Applicants.
COMPLETE SPECIFICATION.
A New or Improved Paste for the Prevention of Discolouration of
Photographs Mounted upon Bristol-board and the like.
We, HERMANN WILHELM VOGEL, of 124 Kurfürsten Strasse, Berlin, Kingdom
of Prussia, Germany, Professor, and JACOB WEINBERG, of 50 Wasserthor Strasse,
Berlin, Kingdom of Prussia, Germany, 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 :---
It is a known fact that photographs mounted on Bristol-board are liable to
become yellow, and all attempts to prevent this have up to the present failed.
Experiments we have made as to the nature of this discolouration show, that it
can only result from the presence of impurities, either in the photographs or in the
Bristol-board. For instance, the silver prints are often treated with too small a
quantity of fixing salt, and the fixing is therefore defective, the following insoluble
compound remaining in the pictures:

page_text: Na,S6J+3 H₂O = Na₂SO¸ + 6 HJ
Experiments have proved that iodine has no noxious effect upon paper photographs
in which the sensitive part of the paper contains silver salts. The experiments
5 have also demonstrated the fact that our improved glue is efficacious in preserving
the photographs for any length of time. It has been further ascertained that the
addition of 10 parts of tincture of iodine (1:10) to 100 parts of starch-paste is the
highest proportion which it will necessary to employ when the paper contains as
much as 1 per cent. of impurities. It will be obvious that the amount of iodine
O which is to be added will in each case depend on the proportion in which impurities
are admixed in the paper, card-board, or photographs.
It will be also understood that our improved glue may be employed with great

page_text: advantage for uniting the several layers composing a sheet of card-board, especially
if such card-board is to be used.for mounting photographs thereon.
It sometimes occurs that the paste or glue is squeezed out laterally of the
photograph to be mounted, thereby occasioning blue spots. In this case we take a
small sponge and soak it in a solution of 1 part of chemically pure sulphite of soda
in 1000 parts of water. The sponge is pressed so as to remove the greatest part of
the solution it has soaked, and is passed over the blue spots; the blue colour will
disappear very rapidly, and it will be sufficient to wipe the moisture away with a
clean piece of cloth.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. As a glue for uniting the several layers of a sheet of card-board, and for
mounting photographs, a paste of starch to which iodine is admixed in solution, for
the purpose set forth.
2. As a means for removing spots occasioned by a glue containing starch and
jodine the employment of a solution of chemically pure sulphite of soda substantially
as described.
Dated this 17th day of August 10,
HERMANN W. VOGEL,
JACOB WEINBERG,
By Geo. Thos. Hyde,
4, Moorfields, Fore Street, London, E.C., Agent for the Applicants.