The portions preferred are the following, viz.—one pound of gutta-percha, six ounces of sulphur, and from six to eight ounces of either magnesia or lime, or a carbonate, or a sulphate of magnesia or of lime, or calcined French chalk, or other magnesian earth. Instead of using the specified proportion of the magnesia or lime, or of the carbonate or sulphate of magnesia or lime, or of calcine French chalk or other magnesian earth, the same proportion of any two or more of these substances combined, may be employed, care being taken that the quantity of this third ingredient in the composition does not vary from the proportion of six or eight ounces. These proportions may, however, be slightly varied, without materially changing the result.
To the composition above specified, a fourth ingredient may be added, viz., gum shellac, by which a still better article will be produced—the body thus obtained being stronger and more easily worked. The quantity of shellac, in such case, should be about four ounces to every pound of gutta-percha.
Resin, oxide or salts of lead or zinc, of all colors, and other like substances, both mineral and vegetable may be added, in small quantities, to either of the above compositions, for the purposes before stated with respect to the India-rubber composition.
The compounds described may be mixed by a masticating machine or other means, until the several ingredients are thoroughly incorporated. The mineral ingredients should be finely divided, and good results are obtained by reducing them before mixture, to an impalpable powder.
When rolled or moulded, the compounds are then to be “cured.” This is effected by exposing the compound to a high degree of artificial heat, using for this purpose either steam, hot water, or hot air. The degree of heat to which this compound is to be exposed, and the duration of its exposure, will depend somewhat upon the size and thickness of the article; but in ordinary cases the heat should be raised to about 260° or 270°, Fah., and the compound exposed to such heat for about four hours; as a general rule, however, it may be stated that the heat should range from 250° to 300°, Fah., and the time of exposure from two to six hours. The compounds or compositions by undergoing this heating or curing operation, will become of a hard, stiff character, in many respects resembling tortoise-shell, horn, bone, ivory, and jet. In the compounds described as compositions of caoutchouc, considerable proportions of gutta-percha may be substituted for caoutchouc (rubber) without injury; and, in the compounds described as compositions of gutta-percha, considerable proportions of caoutchouc may also be substituted for gutta-percha without injury * * * *
The compositions, when hardened, may be worked like wood or bone; but, in some instances, it is proposed to mould, shape, or otherwise treat the compositions so as to render them better suited to the purpose for which they are intended, prior to submitting them to the hardening process. Thus when it is desired to use these new compositions in combination with common flexible vulcanized caoutchouc, the parts intended to be hardened may be united to a connecting band, or connecting pieces of flexible vulcanized caoutchouc, by cementing or pressing together the surfaces required to be joined, before the heating or curing process has been effected; by which means, during the process of curing, the abutting elastic and non-elastic surfaces will become firmly united together.
Another mode of applying the composition consists in uniting them in their plastic or green state with iron, or other metals or rigid substances, which will bear a high degree of artificial heat without alteration or damage, roughened in such portions of its surface as are intended to be brought into contact with the compound of caoutchouc or gutta-percha, and the compound is then applied to the roughened surface of the article. When it is desired that the compound of caoutchouc or gutta-percha shall serve as a covering to the iron or other substance, a thin sheet of the compound (sometimes one thirty-second part of an inch in thickness or less) is pressed with great care, upon the iron or other substance, so as to expel all air from between the adjoining surfaces, and to cause the most perfect union and adhesion, as the coated article is bound with strips or ribbons of cloth, or other suitable material, whereby the compound is kept in close contact with the article during the process of hardening. The combined materials thus treated, will be found to possess the qualities desired—the iron or other substance giving strength and the compound giving a hard and durable surface. In this way may be produced many articles used in and about harnesses or carriages, such as saddle trees, buckles, terrels, bits, stirrups, martingale rings, dasher-irons, and articles intended to be used as furniture, either in whole or in part, and a great variety of other useful objects.
A. Ford. Preparing and dissolving in naptha or oil of turpentine, vulcanized India-rubber for the purpose of water-proofing, and for all or any of the other purposes for which the same not so prepared and dissolved is now applicable, and expressly for the coating of iron ships’ bottoms. Dated June 27th, 1856.
The inventor first cuts the vulcanized India-rubber into small pieces, and places it in a boiler, having within it an agitator or stirrer, kept in constant motion during the process. The only openings into this boiler are a main hole with a screw top; a safety-valve which comes into action only when the pressure on the inner surface of the boiler exceeds 25 lbs. to the square inch, and the opening occasioned by the passage of the stem of the agitator, which passes in at the summit. He then applies heat in such a manner as that three-fourths of the outer surface of the boiler shall be at once exposed to its influence, and at a temperature of never more than 300° Fah.; and he continues the same until the India-rubber shall be reduced to the consistence of dough, when he takes it out, and having mixed with it a sufficient portion of French chalk in powder to remove its adhesiveness, passes it a few times through metal rollers, after which it is capable of being dissolved in naptha or oil of turpentine in the manner of ordinary India-rubber. The rationale of the process is, that by means of the heat applied to the boiler, he decomposes a small portion of the vulcanized India-rubber, whereby a gas is generated which, filling the interior of the boiler, acts upon the remaining portion, and softens it. The not allowing the gas to escape is, therefore, a very important feature.