ZOELLNER'S PROCESS.—An iodide of starch process for reproducing drawings, manu scripts, etc., invented by Dr. F. Zoellner, of Berlin.* Thin and smooth paper of a uniform texture is first to be sized with starch. If paper which was sized with starch in its manufacture is used, the operation is, of course, unnecessary. When dry the paper is sensitized with a mixture of— Concentrated solution sesquichloride of iron i part Concentrated solution ferric oxalate. 6 parts Distilled water 13 parts This solution may be preserved in a dark place and in a well-stoppered bottle for a long time. Floating the paper upon the solution for from 3o to 6o seconds is the best method of sensitizing in this process. The prepared paper may be preserved in portfolios protected from light for over two weeks without losing its sensitiveness.
The exposure, through thin translucent originals, requires in the sun but a few minutes, and in diffused light from 15 minutes to half-an-hour.
The image after the action of the light still remains invisible, but rapidly makes its appear ence with an intense blue color, by treating it with a solution of potassium iodide in diluted albu men. The developing solution is prepared as follows: The whites of two eggs are beaten to a froth, and allowed to stand several hours, then the liquid albumen, which has collected at the bottom of the vessel, is decanted and diluted with one-third of its volume of distilled water. In this diluted solution of albumen 78 grains (troy) of iodide of potassium are dissolved.
The developing solution is applied by means of a wide varnishing brush, and before it is dry is washed off with clear water.
The prints may be developed as soon as they are taken out of the printing frame, or this operation may be postponed for from six to twelve hours. The developed and washed prints are dried in the open air.