Photographic Reproduction Processes (Paperback)

Excerpt: ...The image is bluish-black but weak. After washing the print is immersed in a solution containing 0.5 parts of chloride of gold for 2,000 parts of distilled water, and then fixed in a bath of sulphocyanate of potassium, which tones the image blue-black. It may happen that the proof is slightly tinted red. This arises from a small quantity of lime in the paper which forms uranate of calcium. To prevent the proofs turning yellow, it should be washed in an exceedingly weak solution of acetic acid. If, after exposure, the print is immersed, without it being pg 68 washed, in the gold bath, the image becomes rose-red, but the whites remain pure. The effect is peculiar. H. COOPER'S PROCESS (1865). PREPARATION OF THE PAPER St. Vincent arrowroot200 grainsBoiling water10 ounces Crush the arrowroot to fine powder, then rub it to a paste with a little water, and let an assistant pour a few drams of boiling water while you keep stirring all the time; finally, let him add the rest of the boiling water, the operator still continuing the stirring. The paste is allowed to cool, and will be thicker when cold than when hot. Remove the upper portion entirely when quite cold, otherwise, if any left, it will give rise to streaks. The author insists upon the necessity of all these cares. Two sheets of paper are now placed side by side on a flat board, then the surface of the first is covered with the paste by means of a sponge, proceeding, before you leave it, all over the sheet in a horizontal direction; the second sheet is covered in a like manner. By the time the second sheet is pasted, the first one will be partially dry. The sponge is now drawn over each sheet, in succession, in a perpendicular direction in order to efface the streaks from the first sponging. If the paste drags in a slimy manner, it is too strong, and a fresh arrowroot must be prepared, because dilution only ends in failure. Why dry, the paper is rolled under moderate pressure, and when it lies...