Pyrogallic Acid 1 oz. Water 12 oz. Citric Acid 20 grs. [p023]
Phenix Stock Solution. Keep the Stock Solution securely corked.
Water 4 oz. No. 1 4 drams. No. 2 4 drams.
If the plate be over exposed, add a few drops of No. 3. Should the plate, however, be under exposed, add one dram more of No. 2. When the plate is placed in the developer, the image will begin to appear in from 5 to 10 seconds. Continue the development until the details are all out. _But be careful not to over-develop_, and thereby obscure the shadows. Wash thoroughly after development, and fix in the following solution:
Cyanide of Potass. 120 grains. Water 10 oz.
"Let the plate remain in the fixing basin until every trace of Bromide of silver disappears. Wash well after fixing, and dry with a gentle heat or flow the plate with alcohol for a few seconds. Set it aside, and it will dry in a few minutes without the aid of heat. For varnishing any good negative or positive varnish will answer. Apply a little heat to prevent chilling."
We now take up that more important branch of the collodion process, vis., that for negatives.
The formulæ and instructions already given for positives might enable one to make a negative, but the negatives so made would bear even a remoter relation to one made by the formula about to be given than would a positive made according to these formulæ bear to a good one made by the appropriate means. Important modifications are necessary to reach the highest excellence in either process.
To produce a good negative a collodion is necessary, the film of which is more permeable than that for positives, so that a heavier deposit of iodide of silver may be carried in the film, to the end that in the development a denser deposit of metallic silver may be secured on all parts of the image, but especially on the high lights, which should be sufficiently dense to prevent the transmission of light almost altogether, or at least to exclude the light sufficiently to allow the shadows and intermediate shades to print to the proper depth, while the high lights of the face and such parts of the clothing as are white shall be only slightly discolored.
There are very many formulæ for such collodions, some of which have proved to be eminently satisfactory, and among the best are classed the following: