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.
I further claim, as an entirely new manufacture, the sheet caoutchouc prepared by the within described process of treatment, by the metallic solutions as herein described, as it is thereby so essentially changed in its properties as to bear but little resemblance to such articles as have, heretofore, been manufactured out of the same material, and is rendered applicable to a variety of new purposes hitherto unattempted, or attempted without success.
Nineteenth, to Stephen C. Smith, New York, December 7th, 1837. Manufacture of India-rubber.
Twentieth, to Charles Goodyear, Roxbury, Mass., July 24th, 1838. For manufacturing India-rubber.
Twenty-first, to Nathaniel Hayward, Assigner to Charles Goodyear, Boston, Mass., Feb. 24th, 1839. For an Improvement in the mode of preparing India-rubber for the manufacture of various articles.
Sulphur, it is known, is soluble in the essential oils, which also are the solvents usually employed for dissolving caoutchouc, the oil of turpentine being generally employed for that purpose. I take the essential oil, say oil of turpentine, and dissolve in it, by digestion, a portion of sulphur generally using about a teaspoonful of sulphur, in flour, to a quantity of oil of turpentine which is to dissolve a pound of India-rubber; the exact proportion not being important, and that indicated being sufficiently near for practical purposes. With this solution I proceed as with the ordinary spirits of turpentine.