Extraction from The American Journal of Photography by Various
“A very rapid process to make newspaper illustrations, called gelatinography, is described in the following:
A black glass plate or a tin plate coated with black varnish, as used by sign-painters, is covered with plaster of Paris (gypsum) to a thickness of four-ply cardboard. The plaster of Paris must be of the best quality and reduced to a very fine powder. Add thereto some alum and some sulphate of barium, and in order to prevent the coating from being too brittle, add also a trifle of glycerine or of a gelatine solution.
This mixture must have the consistency of a thin pulp when applied to the glass or tin with a soft camel’s-hair brush.
When dry, the artist may engrave into this coat of plaster of Paris, by means of a lithographic engraving needle, any design or picture with the greatest ease; the plate or glass is thereby laid bare, and design or picture appears black through the plaster of Paris coating. Mistakes or errors are easily remedied by filling in the plaster of Paris preparation.
With the regular printers’ roller composition a stereotype is now made of the picture or design on the glass or plate, in the usual way; some bichromate of ammonia solution should be added to the roller composition, to make the stereotype hard enough for the type press, and it will be as durable as any electrotype, and answer the same purpose.–Am. Lith. and Printer.”
Source: Project Gutenberg
The American Journal of Photography by Various