The Photographic News. Vol. 10, No. 421. September 28, 1866, p.465
DEAR SIR,--I beg you will afford me an opportunity of making a few remarks upon the subject of Mr. Carey Lea's communication to the Philadelphia Photographer, which was reprinted in your journals of the 17th and 24th ultimo, and entitled "An Examination into the Circumstances under which Silver is found in the Whites of Albumen Prints." The writer in question, although anxious to "save others the trouble of making similar investigations," is not probably aware that he has been but repeating experiments, the results of which have already been place a on record. It is four years since the existence of silver in an unsuspected form in the whites--and, indeed, all parts--of albumen photographs was pointed out by me;* yet the author now speaks of it as "a well-known fact, though only lately ascertained;" and proceeds to rehearse, without acknowledgment, my old experiment, by which he finds no difficulty in proving that the albumen-argentic compound is formed in the process of sensitizing the paper, and quite independently of the action of light.
After making this assertion, Mr. Lea proceeds to the trial of a number of chemical substances, with a view to their application as solvents, either before or at the time of fixing, which were found, as in my experiments long since recorded, of little or no practical value in the removal of the silver. So far, then, the results of our separate trials show a general agreement; but Mr. Lea proceeds farther to test the efficiency of various methods of fixing, and arrives at the conclusion that the most permanent photographs, and those containing least silver (or even none) in organic combination, are obtained by the use of the old toning and fixing bath of hyposulphite of soda to which chloride of gold has been added. From this opinion I entirely dissent, and give my reasons for so doing. Firstly, because the pictures produced in this way are, as a rule, discoloured in the whites, and cannot therefore show in so marked a manner the yellow stain due to the action of the test--sulphide of ammonium. Secondly, because a lengthened experience of this identical process (which was in common use from seven to ten years ago) has always given me proofs in which the amount of argentic compound exceeds that contained in the pictures of to-day, produced by methods in which the toning and fixing agents are applied separately. It is possible that the specific instructions given under 10** for the preparation of a hot solution of gold and hyposulphite, which is to be "used two or three hours after mixing," imply that it may be somewhat above the common temperature when the prints are immersed, and so may partake of the advantage necessarily resulting from the greater solvent powers of the hyposulphite under such circumstances; but, on the other hand, this effect is always attended with a general loss of vigour, and entails a proportionately longer exposure in the printing-frame.
By the use of this bath it is said that in one instance "a print was obtained of which the whites were perfectly free from silver." With regard to this statement, I would direct attention to the fact that the first and last proofs of any batch immersed in succession in the same fixing solution differ widely in respect to the proportion of silver retained in the whites; and although I have been able to produce single pictures, or a small parcel, comparatively free from silver, by the use of an extremely liberal amount of the hyposulphite, or other fixing agent, it is manifest that the principle is not capable of extension to commercial operations on the score of cost. We still require some supplementary agent--such as the carbonate of ammonia, or a better one, if it can be found--to augment the solvent action of the hyposulphite; and of all the substances available for this purpose, I should condemn, from the results of my experience, the use of terchloride of gold. The writer seems, indeed, to admit, in his concluding paragraph, that he has failed in the object of his search, for he says:--" It follows, therefore, that no substance (as far as these experiments go) is capable of dissolving out the silver from the albumen."--I am, &c., Woolwich, September 22, 1866. JOHN SPILLER.