I have sometimes covered the surface of the caoutchouc with the metallic powder known by the name of bronze, and have afterwards washed it over with nitric acid, which has produced the same effect as the washing it with, or dipping it in the metallic solution, such a solution being in this case immediately produced by the action of the acid upon the metal. It is a common practice to add some of the absorbent earths, or some pigment, to the dissolved caoutchouc, and when this is done the metallic solution may be readily made to operate to a greater or less extent throughout the whole mass of a sheet of considerable thickness. Instead of the process above described, or preparatory to it, I combine the caoutchouc with quick lime, as I have found this earth is preferable, in fitting the sheet caoutchouc to be acted upon throughout its whole thickness by the metallic solution; but besides this, the lime has the property of bleaching the caoutchouc, and of giving to it a surface and texture adapting it to the receiving impressions from copper plates, or by other modes of printing, rendering it, either alone or when used as a coating for cloth, applicable to the purpose of printing charts, or other devices. The caoutchouc so prepared with lime, will be rendered adhesive by the action of heat or of solvents, unless the metallic solutions be applied to it; in which case much of the whiteness communicated to it by the bleaching property of the lime will disappear. The following is the process: I slake a portion of the finest quick lime, and then mix and agitate it with so much water as that it shall not be thicker than milk, when on allowing it to stand at rest, all the coarser particles contained in it will rapidly subside; the upper portion containing the finer particles, is then to be poured off, and the fine lime allowed to subside, the water left on the surface of this being poured off, it is obtained in a state fit for incorporation with the caoutchouc when in that form of thick paste into which it is brought by the manufacturer, preparatory to its being rolled into sheets. What I claim as my invention, and wish to secure by letters patent, is the destroying of the adhesive property not only of the surface of caoutchouc, gum elastic, or India-rubber, but also to a considerable extent below the surface, whether the same being in sheets unconnected with cloth, or other substances, or when used as a coating therefor, by the application thereto of an acid solution of the metals, substantially in the manner set forth. I also claim the manner of preparing and incorporating lime with the caoutchouc paste, for the purpose of bleaching it, and giving to the sheets formed of it a color and texture adapting it to receive printing impressures and rendering it applicable to various other purposes, either without or with the treatment by the metallic solutions, as set forth.