PLAIN (SALTED) PAPER PRINTING This employs a paper sensitised by immersing in a soluble chloride, and floated afterwards in a bath of silver nitrate. The paper is either only slightly sized or not sized at all, with the result that the original surface or texture of the paper is retained, and the prints appear to be on plain paper, hence the term. Such papers are printed out under a negative in daylight, and then toned and fixed. Good writing paper serves well for small prints and Whatman's or any other good drawing paper for large ones. When sizing is omitted some workers add just enough potassium bichromate to the salting solution to colour it faintly.
Arrowroot and gelatine sizes appear to be the most popular. For the latter use Gelatine . . . 100 grs. 23 g.
Chrome alum . 4 ,, Ammonium chloride . 5o ,, Water . . . 10 oz. 1,000 ccs.
The gelatine is soaked for thirty minutes in 8 oz. of the water (cold) and the chrome alum dissolved in the remaining 2 oz. The gelatine is next heated on a water bath, the ammonium chloride stirred in, the whole strained through fine muslin, the chrome alum solution poured very gradually into it, and the whole stirred. It is now ready for coating upon the paper, and should be stood in hot water to keep it fluid. The paper is pinned to a flat board or laid upon glass and weighted at the corners. The salting solution is sponged on as quickly and as evenly as possible, being finally gone over with a squeezed sponge tp remove superfluous solution. Three minutes should be ample time in which to salt a 2o-in. by 16-in. sheet ; and the quantity of solution above given can be made to coat ten such sheets. They should be kept flat for a few minutes until the gelatine has penetrated, and then hung up to dry in a warm place. The pre pared paper will keep good for several months.
When required, the paper is sensitised with a silver nitrate solution : Silver nitrate . . boo grs. 138 g.
Citric acid ,, 69 Distilled water . . To ozs. loco ccs.
Sensitising is done in a weak or yellow light' and the mixture is applied by floating, or pre ferably by brushing, and not by total immersion. Any brush used must be in wood and not in metal. Apply the sensitiser evenly and liberally, and hang the coated paper in a warm dark place for about ten minutes in order that it may become surface dry, and then repeat the applica tion in order that there may be an excess of silver nitrate, which is necessary for rich and brilliant prints.
Printing can be done from almost any kind of negative, thin or flat ones being the least suit able. The prints lose but little in toning and fixing, therefore the printing need not be carried very far beyond the result desired. When taken from the printing frames, the prints should be well washed, say, for fifteen minutes, to re move the acid and free silver salt, and are then ready for toning, for which any gold or platinum bath may be used if weakened with water, the following being specially recommended : Sodium acetate . . 3o grs. 4 g.
Gold chloride . . I gr. 13 Water . . . 16 oz. s,000 ccs.
Mix about twelve hours before use. Toning is very rapid, one minute's immersion giving, as a rule, the best brown or sepia tones. Over toning is the commonest cause of failure, but as prints always dry a colder tone than they appear when wet, allowance should be made. The toned prints should be placed in a solution of + oz. of common salt in 6o oz. of water, in order to stop the toning action they are next washed for a few minutes, fixed for ten minutes in a " hypo " bath, and finally washed again.
Alternative Baths.The following is a good sensitiser : Silver nitrate . . 600 grs. 138 g.
Water . . . . so oz. s,000 ccs.
Add liquor ammonia drop by drop, until the precipitate first formed is dissolved.
The following sensitiser is suitable for papers sized with arrowroot ; in the case of agar-agar papers the citric acid should be increased to 300 grs. or 117 g. : Silver nitrate . . 14o grs. 164 g.
Citric acid . 55 ,, ,, Distilled water . . 2 OZ. 1,000 ccs.
Alternative toning baths are as follows : I. Potass. chloroplatinite 20 grs. 4.5 g. Nitric acid . . so mins. 2 ccs.
Distilled water . so oz. I,000 Tone and fix as usual.
2. Citric acid . . 36 grs. 8 g.
Common salt . . I 2 2.7 Potass. chloroplatinite I gr. 23 Distilled water . so oz. s,000 ccs. Tone and fix as usual.
3. Borax . . . 3o grs. 7 g.
Gold chloride . . f gr. 1 Distilled water . so OZ. 1,000 COS. Use as soon as mixed; tone and fix as usual.
4. Sodium phosphate . so grs. 2 g.
Gold chloride . . I gr. I Water . . . so oz. I,000 ccs. Use as No. 3, above.
The following is a plain paper which may be called " self-toning," as excellent tones may be obtained simply by fixing in a 2+ per cent, solu tion of " hypo "say, I2 grs. to 1 oz. of water. The paper (without water-marks) is given an extra coating of size, made by rubbing up 90 grs. of arrowroot with 5 oz. of cold water, adding a solution of 20 grs. of glucose in 5 oz. of hot water, and boiling in an enamelled saucepan for two minutes. When cool, immerse the paper till thoroughly saturated, dry, and sensitise with Nelson's gelatine . . 6o grs. 14 g.
Tartaric acid. . . 8o 18.5 Silver nitrate . . 90 21 Ferric ammonio-citrate . 400 ,, ,, Water . . . . so oz. 1,000 ccs.
The solution, made as described earlier in this article, should be stored, if required, in a black bottle. After proceedings are as already de scribed.