In our practice we have often taken a negative cliché from drawings made in the ordinary manner, without the aid of the camera obscura (which would have been too expensive for drawings of a certain size), by simply printing a proof by contact on plain or albumenized silvered paper, and fixing, without toning, in a new solution of sodium thiosulphate, then washing as usual. The proofs thus obtained from designs drawn with an opaque ink, which allows a long insulation and, therefore, yields an intense reduction, are of a deep brick-red color, quite non-actinic, and give very good positives by the Artigues process.
N.B.—Paper in drying never assumes its original shape; it is, therefore, necessary to make the figures on the reproductions from plans when they are not on the originals.
CHOICE OF PAPER. SIZING.
In all the photographic processes by precipitation of metallic oxides the quality of the paper has a great influence on the results. When the paper is not well sized and not well calendered, the sensitizing solution is absorbed, instead of simply impregnating the surface of the paper, and not only the image is sunk in and its sharpness impaired, but good whites can never be obtained, especially if the image should be toned, owing to the impossibility of eliminating the metallic salts not acted on, that is, not reduced by the action of light which the fibers of the paper mechanically retain.
The “endless” rolls of paper, 54: inches wide—or “blue print paper,” as it is sometimes termed—of Blanchet fréres et Kléber, of Rives, better known as “Rives' paper”, that of Johannot, of Annonay (France), and the Steinbach (Saxe) paper are recommended.
For small prints from negatives in half tone the positive paper, 18×22 inches, of Rives or Saxe, should be preferred to the heavy kind. It is advisable to size it, so that the impressions be entirely formed on the surface of the paper. Moreover, an additional sizing is always advantageous, whatever be the photographic process employed, to prevent the imbibition of the sensitizing compound and to obtain more brilliant and [pg 28] vigorous images, for the iron, chromium, uranium and other metallic soluble salts require the presence of an organic matter (alcohol, ether, gum arabic, glucose, caseine, etc.) to be reduced by the agency of light; and as a consequence, the greater, within certain limits, of course, the amount of organic matters, and the more thoroughly they are mixed with the salts, the more sensitive the preparation and the better the results.
Arrowroot is the best sizing for our purposes. Gelatine may be employed, albumen also, but the coating should be insolubized when applied on the paper and dry.
Sizing with Arrowroot.—In a porcelain dish diffuse 4 parts of powdered arrowroot and one part of liquid glucose in 200 parts of distilled or rain water and dissolve by heat over an alcohol lamp, stirring all the while. Let the solution boil for an instant, and when the paste is homogeneous let it cool down and then remove the skin formed on its surface and strain it through a fine canvas. Now provide with three small sponges free from gritty matters and cleaned in water, and nail by the four corners, one over the other, felt size uppermost, as many sheets of paper as you wish to size on a board somewhat smaller than the paper. This done, with one of the sponges take a small quantity of the arrowroot and, brushing it length-way and cross-way, spread the paste into an even layer, then, by rubbing very lightly with the second sponge, efface the striae and smooth the coating as well as possible. The third sponge serves to remove the excess of paste when too much is at first spread on. From six to seven sheets of paper, 18×22, can be sized with the quantity of arrowroot paste above given.
Another, but not quite so effective a manner of sizing although sufficient for the cyanotype, is the following, employed by Mr. Pizzighelli for the paper used in the platinotypic process:
Ten parts of arrowroot are powdered in a mortar with a little water and then mixed by small quantities to 800 parts of boiling water. After a few minutes 200 parts of alcohol are added and the mixture filtered. The paper is immersed for two or three minutes in the warm solution and hung up to dry.