36. Mount Street, Grosvenor Square.
PHOTOGRAPHIC CORRESPONDENCE.
Mr. Lyte's Treatment of Positives.—It would be quite superfluous, after the very excellent communication of Mr. Pollock, were I to give a detailed account of my method of printing albumen positives, as, in the main, we both follow the process of Mr. Le Gray. But as we both have our own improvements on the original process, I will ask for space in which to record our differences in manipulation.
First, in regard to the chloride of gold, I always find, and I believe such is the experience of many photographers, that all salts of gold, though they heighten the effect at first, have a slow, but sure, destructive action on the picture.
Next, I find that acetic acid, by generating sulphurous acid, has a similar effect, and my care was to try and make a solution which should be free from these defects. I first take my positive, which, as a general rule, I print at least half as dark again as the shade required. This done, I wash it well with water, and next with salt and water in the proportion of about half a grain per gallon, or quite a tasteless solution; this removes all the nitrate of silver from the paper, or if there is any left, the bath of salt decomposes it, leaving none in the texture of the paper to unite with the hypo., which otherwise forms a sticky substance, difficult to remove, which may be readily seen on looking through a positive which has been too hastily finished in the usual way, giving a dark shade, and a want of transparency to the lights. I then place the picture in a bath composed as follows:
Sodæ hyposul. 3 oz.
Argent. chlorid. 70 grs.
Potassii iodidi 5 grs.
Pyrogallic acid 1½ to 2 grs.