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Most Viewed- The Primuline Or Diazotype Process- The Black Or Ink Process Ferro-tannate Process - The Cuprotype Burnett's Process - The Uranotype - A Poitevin's Process 1870 - The Aniline Process - The Carbon Process - The Cyanofer Pellet's Process - The Cyanotype Or Blue Process - Choice Of Paper Sizing Least Viewed- Preparation Of Red Yellow Or Blue Tissues- Godefroy's Process 1858 - X's Process 1865 Secrets Of The Uranotype - L Liesegang's Process 1865 - Guarbassi's Process 1867 - H Cooper's Process 1865 - How To Make A Negative Drawing - Tracing Process On Metal - Cj Burnett's Process 1857 - Printing On Wood Canvas Opal And Transparencies |
The Black Or Ink Process Ferro-tannate ProcessThis process gives black positive impressions on white ground from positive cliches, and negative impressions from negative cliches. It has been attributed to Mr. Colas, but in reality it was invented by Mr. Poitevin, who describes it as follows in his communication of May, 1860, to the Societe Francaise de Photographie: "I make a solution containing--" Iron perchloride, cryst 10 parts Tartaric acid 3 parts Water 100 parts "I apply the paper on this mixture and let it dry spontaneously in the dark, and at the moment of using it I completely desiccate it at a gentle heat. Thus prepared the paper is of a deep yellow color. Light decolors it rapidly, and ten or twelve minutes' exposure through a positive cliche suffices to well impress it, that is, to reduce in the whites the iron perchloride to the state of protochloride." "To print, one is guided by the decoloration of the paper, and even for more facility I add to the solution of iron perchloride and tartaric acid a small quantity of a solution of potassium sulphocyanide for the purpose of obtaining a red tint, which is more visible and disappears also under the influence of light in proportion to the decomposition of the perchloride. One obtains then after exposure a red design on the white ground of the paper. This red color is not permanent. It even disappears by keeping the proof in the dark." "To develop and then to fix the design thus obtained I wash rapidly the paper in ordinary water, or better, in water holding chalk in suspension. The red coloration disappears, a part of the iron perchloride is washed out, and in the parts which have not been acted on by light the perchloride is transformed into sesquioxide. I replace then the water by solution of gallic acid or of tannin and the image progressively appears in ink-black. When I judge the image to be sufficiently intense I wash the proof in rain water, in preference to ordinary water, which might cause the gallic acid and tannin to turn brown. I sponge between sheets of blotting paper and let the proof dry spontaneously." "If in place of gallic acid I use a diluted solution of potassium ferricyanide (red prussiate of potash), Prussian blue is formed in the parts acted on by light. The preparation is even sensitive enough to permit one to obtain an impression in the camera obscura in developing by the ferricyanide." "As to the proofs in gallate (or tannate) of iron, they can be transformed into Prussian blue in a solution of potassium ferrocyanide (yellow prussiate of potash) slightly acidified by sulphuric acid." The paper most suitable for this process is that which has been previously well sized with starch, as explained in a special paragraph of this pamphlet. Paper prepared with a film of coagulated albumen gives also good results. It may be prepared by brushing as well as by floating, but in either case the paper should be wetted on the surface only and dried rapidly at a temperature of about 115 deg. Fahr. (46 deg. C.) and kept in a dry place. It does not keep for more than from ten to fifteen days, owing to the hygroscopicity of the iron compound. Mr. Colas, who prepares the paper for the Parisian market, I think, states that he avoids its deterioration by keeping it wrapped in blotting paper, between two sheets of India rubber, to exclude air and dampness. Silvered albumen and plain paper, well desiccated, could be kept in that way for a certain period, especially if the blotting paper is impregnated with sodium bicarbonate and well dried. Mr. A. Fisch advises to discard the preliminary washing and to develop just on the removal of the proofs from the printing frame. In operating in this manner the development is best made by floating, taking care that the solution does not run off the back of the proof. The developer may consist of a dilute solution of nutgalls or of Tannin or gallic acid 4 parts Oxalic acid 0.15 parts Water 1,000 parts After developing the proof should be washed rapidly--under a jet of water, if possible--for were the iron salt and the reagent not soon removed, or any remain in the paper, the ground would be tinted violet. And whatever be the care taken, it very seldom occurs that the whites are pure when the proof is dry. This for half-tone pictures has not a great importance, but for the reproductions of plans it is sometimes objectionable. In fact it must be acknowledged that none of the processes now at our disposal--if we except the so-called Artigues process described further on--gives an entirely satisfactory result. A simple and expeditious process, yielding intense black impressions on a white ground, is yet to be found for the reproduction of plans, maps, etc., without resorting to a negative cliche or drawing. Next: The Cuprotype Burnett's Process Previous: The Cyanofer Pellet's Process
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