(2) Gelatine . . . . . . . . . 20 gr.
Sodium Chloride . 3o „ Water • . . . . . . . . 5 oz.
(3) Arrowroot 90 gr.
Ammonium Chloride . . . 6o „ . . . . . . . . . to oz.
Make up the arrowroot into a paste with an ounce of cold water, and dissolve the rest with the chloride in hot water. The paper must be floated for three minutes on one or other of these sizing baths while they are still warm, and then hung up to dry.
Sensitising Bath.—This may be either the bath given for albumenised paper, which will be the best for use with sizing solution No. I. But almost equally good effects can be got with those given below.
(1) Nitrate of Silver . . . . . . so gr.
. . . . . . . . . 2 oz.
To which sufficient ammonia has been added drop by drop until the precipitate at first formed has been redissolved.
For Keeping Purposes.
(2) Nitrate of Silver . . too gr.
Citric Acid . . . . . . . . . 3o „ Water Distribute the sensitising solution evenly over the paper with a broad camel-hair brush, or float in the manner given under albumenised paper for three minutes. Then dry in the dark.
Porous papers require rather more gelatine (say one-third more) than hot-pressed papers. These plain, salted papers on well in the sodium-acetate bath given above, but the best effect, especially with drawing papers, is obtained with Clarke's platinum-toning formula : Potassium Chloroplatinite . . . . . to gr.
Nitric Acid . . . . 5 min.
Water . „ . . . . . 25 oz.
The fixing bath may be the same as that given for albumen paper. Combined toning and fixing baths (which
we do not recommend with albumen) work fairly well with these papers.
Resinised Papers.—The late Mr. Henry Cooper com municated to Sir W. Abney a printing process, the results of which have a character of their own, lacking the gloss of albumen. If printed deeply and toned in acetate this paper has almost the appearance of fine old porcelain. Coat with the following : Frankincense . . . . . . . to gr.
Mastic . . . . . . . . . 8 „ Calcium Chloride . . . . . . 8 „ Alcohol . . . . . . . . . I oz.
The sensitising bath consists of 60 gr. silver nitrate to the ounce of water, with as much gelatine added as it will bear at Fahr.
Self-toning Papers.—Several papers of this class have been placed on the market during the last few years, and some formula have been published. Only the very recent brands, however, are satisfactory, either for their toning or keeping qualities, and the manner in which the gold is pre served in contact with the other ingredients is of course the makers' secret. The Paget Collodio-chloride, the Ilford Kalona, and the Kodak Solio self-toning papers will all be found good. The instructions in each case differ considerably, but as a rule such papers, after very deep printing, are placed direct in a weakly alkaline bath, and then fixed in the ordinary hypo bath, a variation in tone being obtained by a short stay in a weak solution of common salt.