Indiarubber and Gutta-Percha — Mending Indiarubber Shoes and making Garments Waterproof, with other Applications
Indiarubber or gutta-percha enters into so many familiar and useful objects that there are few people who would not like to know how to repair them when injured.
Like the brittle or non-elastic gums, caoutchouc (with which I include the nearly allied gutta-percha) is greatly modified by admixture with certain pulverised substances, which form with it a partly mechanical, partly chemical, combination. Those who would thoroughly study the subject in all its relations may consult Kautschuk (Caoutchouc) und Guttapercha, von Raimund Hoffer; Wien, 1892, Hartleben.
Caoutchouc is partially soluble in carburetted sulphur, ether, pure petroleum, or benzole, but gutta-percha is perfectly so. In this state it may be applied as a varnish or coating for repairs, as it hardens by exposure to the air. When mixed with sulphur and exposed to a heat of 110° to 115° centigrade, gutta-percha becomes what is called “vulcanised,” assuming a very light grey colour, is more elastic, and retains this elasticity at a much lower grade than before. When the heat is raised to (maximum) 180° the mass becomes very hard, tough, and black, or like horn. The conditions of its toughness, elasticity, and hardness depend upon the amount of sulphur used; as in other combinations, the harder the material becomes the less elastic it is—that is, the more brittle.
Ebonite is extremely hardened caoutchouc. It is first treated with chlorine, washed with sulphate of soda infused in water, and finally mixed with hardening substances and submitted to severe pressure.
As indiarubber or “gum” shoes are in general use, most people would consider them the proper objects to begin with. To do this, first make two separate preparations as follows: