PAPERS.
When I say plain papers I mean, of course, papers without a superficial coating of gelatine or albumen. In the choice of these for salting and sensitizing there is no restriction except that of chemical purity, and no difficulties in manipulation greater than will be met with in any other printing-out process.
Bromide " matt " papers do not come under this heading, since the gelatine surface is only made " matt," or free from glaze, by the use of starch, resin or other admixture in the coating of the paper. Platinotype is a typical example of a " plain " paper, and similar results may be obtained by the use of silver salts instead of platinum, with the additional advantage of a far wider range of color and texture than is possible in that process.
Your paper should be chemically pure and particularly free from iron spots (which, when the paper is sensitized, will spread out like asterisks,) and at the same time it should be selected with your ultimate aim as to effect well in view. The purest I have found, next to " Rives," on which platinotype is coated, and for the matter of that most silver papers, too, is \Vhatman, which is sold in three grades, viz. : H. P., hot pressed or smooth ; N., not, and R., rough, and then come Arnold, Harding and Hollingworth, all of which may be obtained from the principal Artists' Colormen without any difficulty and in various sizes. " Royal " measures 24 x 20 in. and Imperial 31 x in.; and costs from 3d. to 6d. a sheet, according to its weight. These sheets can be cut up to the sizes you wish to yrint, allowing a little margin to handle them by in salting and sensitizing.
Having decided upon the paper you wish to use, a salting bath is made up as follows : Common Salt, - - - 5o to ico grains.
Gelatine, - - - - - to grains.
Water,- - - to ounces.
But this again is a variable quantity, soft and porous papers requiring more gelatine to size them than hard, rough surfaces will take up. The bath should be used hot, so that it is thoroughly absorbed. The exact time of immersion—for the paper is put in bodily, not floated—does not matter, and it will be often found necessary to let the first sizing dry and then to give a second bath later on, that the pores of the paper may be well filled up.
You can salt half a dozen or more sheets at once, turning them over from time to time and then hanging them up by American or other wood clips to dry.
At this stage the paper will keep indefinitely, but it is as well to keep it under pressure that it may be easier to manipulate in the subsequent process of sensitizing. The stronger the salting the weaker may be the sensitizing, and there is room for considerable variation in both according to the character of the negative you are going to print from and the result you want to get.
The paper is now ready for sensitizing, and this is done on any of the ordinary silver baths used for albumenized papers, the standard being oo grains Nitrate of Silver, to oz. of Water(preferably distilled) and 1,5 grains of Citric Acid.
This, with occasional strengthening, will last for a long time kept in a dark place in a stoppered bottle.
Take your salted paper by the right hand corner and float it on the bath, using gentle pressure at the same time to exclude air bubbles, (which would come out as insensitive spots in printing), leave it floating for 2 or 3 minutes, then hang up to dry in a moderately dark room until it is ready for use.
I have found it always better to sensitize paper slightly damp, since one can get a more even coating, and the edges do not curl up in the provoking manner common to papers when dry, but care should be exercised to avoid the sensitizing solution coming on to the back of the paper.
This is done in the ordinary manner in a pressure frame, but the image may be taken rather darker than with ordinary albumenized papers to com pensate for subsequent loss in toning and fixing. But be sure to varnish your negatives before printing, to avoid staining them. I cannot explain it, but the fact remains that although I have never had staining occur with albumenized papers, with the use of strongly salted and sensitized drawing papers, such an occurrence has been frequent, and although there are several reputed cures for such staining, I never yet found a satisfactory one.