Albuminised Paper. There are several well-known papers sold; Rive’s, which is a French paper, has a high glaze and fine surface; the Saxe, which is more uniform in its texture, is made in Germany. Another maker is Towgood. Positive paper is albuminised by placing it in a mixture composed of white of eggs and salt. To the white of each moderate-sized egg use 15 gr. of common salt reduced to a fine powder; whisk until the albumen is all white froth. Leave this froth in a glazed earthen pan for about 12 hours, by which time most of it has settled into clear albumen; pour the clear portion into a flat porcelain tray. This tray should be somewhat larger than the sheets of paper to be albuminised. Lift the paper up by the ends and lay it carefully on the albumen, keeping the side marked as “inferior” uppermost and dry.
The paper should be slightly damp before it is thus treated, as it then takes the albumen more regularly, and is not so liable to air-bubbles. The paper must be lifted at each end, and should any air-bubbles appear, brush
them off with a card or small brush, replacing the paper in the bath. Wherever the albumen does not come into actual contact with the paper, a white mark will appear in the print. Remove the paper from the bath and place it to dry on a cardboard frame, or suspend it at the corners by clips. Paper glazed with pure albumen acquires too brilliant a glaze for portraits; the albumen may be diluted with from a 1⁄4 to 1⁄3 its bulk of water. It should be kept in tin or zinc cases.
Plain Paper. Albuminised paper may be used as plain paper if, instead of sensitising the glazed side, the plain side is placed in the sensitising solution.
Nitrate of Silver Bath (for Negatives). Recrystallised nitrate of silver, 1⁄2 oz.; distilled water, 7 oz.; collodion, 7 drops. Shake well together until the crystals have dissolved, then filter.
The purity of the negative bath is a matter of great importance, hence the necessity of employing the very best nitrate of silver, and also of excluding all foreign matters of every kind. When the bath gets out of order, it should be diluted with an equal bulk of distilled water, and exposed to the sun for a few days, in a white glass bottle, then filtered, and sufficient nitrate of silver added to restore the strength to 35 grains an ounce, as indicated by the argentometer.
The Argentometer. This instrument is for ascertaining the strength of the nitrate of silver solution, which becomes weakened to a certain extent, after the immersion of every plate.
Developing Solution (for Negatives). Protosulphate of iron, 75 gr.; glacial acetic acid, 2 dr.; alcohol, 2 dr.; distilled water, 5 oz. Dissolve the crystals in the water, then add the acid and alcohol, and filter. In hot weather a little more acetic acid may be added, and if it does not flow readily, the alcohol may be increased.
Intensifying Solution, No. 1 (Negatives). Pyrogallic acid, 10 gr.; citric acid, 10 gr.; distilled water, 5 oz. When it becomes brown it is useless. No. 2. Recrystallised nitrate of silver, 40 gr.; distilled water, 1 oz.; dissolve and filter. This latter will keep for any length of time in the dark.
Another Intensifying Bath (Negatives). A saturated solution of bichloride of mercury in water. Place the negative plate in a bath of the solution, remove when the film assumes a milky-white appearance, wash, and then plunge into a solution of 1 oz. of liquid ammonia to 10 oz. of water. Remove the plate, wash, and place to dry. This mode of intensifying may be regulated by leaving the plate in the bichloride of mercury a shorter time, when it will require a weaker ammonia bath than that above given.