The Photographic News. Vol. 10, No. 415. August 17, 1866. p.394

AN EXAMINATION
INTO THE CIRCUMSTANCES UNDER WHICH SILVER IS FOUND IN
THE WHITES OF ALBUMEN PRINTS.

THE last two years have witnessed the most serious assaults that have ever been made upon silver printing, and for a time with every prospect of immediate success. Nevertheless, the old process is just as fixed as ever, and there seems as yet little prospect that any of the novelties so vaunted will secure even a humble share of the work. Not that I have the least disposition to undervalue carbon printing. I earnestly hope to see the day come when it will entirely replace chloride printing. Mr. Swan and Mr. Pouncy have produced some specimens of work of beauty so extraordinary, as, in my opinion, to have surpassed the best silver printing. And some specimens of Mr. Woodbury's relievo printing are extremely good. But something easier, simpler, and more certain will have to be thought out before the old method becomes antiquated. So long as it does not, it will be a matter of unceasing regret that any doubt should exist as to the perfect permanency. To purchase an exquisitely beautiful photograph, and, after a time, to see that fatal yellowness stealing over the high lights, and to know that its final destruction is only a question of time, is a real vexation. Fifteen years ago I purchased, when abroad, a number of Roman photographs, not one of which is now worth the paper on which it is printed; and every one has had similar experience.

It, therefore, is clear that the two directions in which study can be most profitably directed for the advancement of photography, are, in the simplification of carbon printing, and in the determination of all the causes of deterioration to silver prints.

It is a well-known fact, though only lately ascertained, that silver exists in the whites of albumen pictures. I have carefully studied the conditions of its presence, and, without being able to make so satisfactory a report of results as I could wish, I hope to have done something towards extending our knowledge in this direction.

Before proceeding to detail the results of individual experiments, I may mention one general fact. It has been asserted that the existence of silver in the whites was due to the action of faint light, passing through the darkest parts of the negative--light too faint to visibly darken the chloride of silver, and thus impair the whiteness of the high lights. I have disproved this in the following manner: A piece of albumenized paper was sensitized at night, dried, washed, and fixed, without any exposure, under a negative. It was, of course, snow-white. Tested with sulphydrate of ammonia, it gave indications of silver, just as well-marked as other pieces exposed under a negative, and fixed and toned in the usual way. There can exist, therefore, no doubt that the presence of silver in the whites is owing to a combination formed at the time of sensitising, and that it has nothing to do with the exposure.

I have also remarked another fact which has its importance, and which, if not duly borne in mind, may lead to erroneous conclusions. It is, that even dilute sulphydrate of ammonia will make a very evident mark upon albumenised paper which has never been sensitised, and which consequently does not contain a trace of silver. While wet, this mark is yellowish, and so exactly simulates the appearance produced when a faint trace of silver is present, that even a careful observer might be deceived. Even after drying, the mark does not disappear. The yellowish colour of course is gone, but there remains a dead mark that contrasts with the brilliance of the general albumen surface, and this all the more strongly, as the dead mark is surrounded by a bright border, brighter even than the rest of the albumen surface.

When testing, therefore, in this manner, it is necessary to let the mark made by sulphydrate of ammonia become completely dry before judging of it; and also to bear in mind, in the case of very faint marks, that their intensity is increased in appearance by the great alteration of surface caused by the reagent.

I shall next proceed to give the comparative results in the examination of the condition of the whites in a great many different tonings. To make the results fairly comparative, the following method was resorted to. A large negative, highly intensified, so that the high lights were perfectly protected, was printed. A number of different toning baths were prepared, and got into working order together. The print was washed, then cut up, and different pieces were toned in the respective different baths, were fixed with hyposulphite of soda, and, after drying, were tested with hydrosulphate of ammonia. The specimens thus obtained--some as far back as last winter, and others at various times--were carefully indorsed and noted, and are now before me as I write. In all cases when the contrary is not stated, the prints were made on ammonio-nitrate paper.

1. Toned in the citrate of gold bath. Fixed in hypo.--. A camel's-hair pencil or clean pen dipped in dilute sulphydrate of ammonia, and drawn over the whites of this specimen, left a clear buff mark of sulphide of silver.
2. Toned with benzoate of gold as described by me.-- Result the same as the last.
3. Sulphur toning (trithionate toning), obtained by adding chloride of lead to hyposulphite of soda.--This toning, with or without the addition of gold, is sometimes used still for obtaining intense blacks upon plain paper. It is, of course, not to be recommended, and is included here for greater completeness. Here a larger amount of silver seems to be left in the albumen, for the application of the sulphydrate caused a much deeper mark than in the preceding.
4. The next trial was made with the well-known old toning and fixing bath of hyposulphite of soda, to which gold has been added. On treating the white with sulphydrate of ammonia, indications of silver were obtained, but much less than in any of the preceding. The streak, in fact, was pale yellow.
5. The lime toning.--The indications of silver in this case were but moderate.
6. Alkaline chloride toning gave results not varying materially from the last.

The trials in three of the above tonings were repeated subsequently. The citrate and benzoate of gold gave the same results as above stated. The third was the fixing and toning bath of hypo and gold. In the trial above given, it is mentioned that the mark, in its case, was much paler than in the others. In the repetition, a print was obtained of which the whites were perfectly free from silver. After the mark of sulphydrate was dry, it could not be found.

^* Philadelphia Photographer.