Caoutchouc (India Rubber)

Caoutchouc.

CAOUTCHOUC of commerce comes from South America and Africa — in bottles from the former, in huge agglomerations from the latter. There is also an East India variety, but it is little known. As the trees are not exhausted by giving out their sap, there would seem to be no fear of a failure of future supply, no matter how great may be the demand. The Para caoutchouc, or that which comes from South America, is freer from impurities and worth a higher price in market. While the African is worth from fifty to ninety cents a pound, the Para will vary from one dollar to one dollar and a half.

The manufacture of caoutchouc is very simple. It is first washed. This is done by soaking and softening it in water and then flattening it into thin slices, a yard long by a foot wide, under powerful iron rollers. After being dried by exposure to the air, these slices are "masticated" — that is, they are thrown inside an iron case, where revolving iron rollers with serrated surfaces chew and tear and grind the slices until they force themselves like bulging pillows out an aperture. At this a workman stands ready to tuck and re-tuck the pillowy substance back again within the grinders, to be torn in pieces and chewed again. This process goes on and on for hours, until the caoutchouc is white as cream and sticky as pitch. It is then removed to a hydraulic press, from which, after a pressure of eight and forty hours, it comes out a solid block of pure gum, worth from $3 to $5 per pound.

Thus far it has not been vulcanized. For many articles vulcanization is not needed; and by means of a sliding cutter, capable of adjustment to the thousandth part of an inch, sheets out of which these articles can be made are shaven from the block. Tobacco-pouches, hospital-sheets, surgical bandages, thread, letter-bands, etc., which are to be used where exists an equipoise of temperature, would not be improved by vulcanization.

Now, for making vulcanized goods, such as garments, hose, tubing, steam-valves, etc., this solid block of pure gum is melted, and there are mixed into the molten mass coal-dust, lamp-black, and soot, in the proportion of from three to eight parts of foreign material to one of India-rubber. Into all this thrown sulpur [sic] sulfur, and then heat is applied up to 300 Fahrenheit, when the whole is ready for use. It may be spread upon cloths for garments, or cast into molds for valves, or piled every other layer upon canvas for engine-hose, or poured into tubes for piping, or cast into a solid block for being cut into various articles. It is still india-rubber, though four parts out of five are of foreign ingredients. It is more elastic, of better color, as free from smell; it will neither tear nor crease nor shrink nor decay; it is a leather that will not crack, a metal which will not break, a cloth that will no be soaked.

There is another method. After pure caoutchouc ahs been melted and spread, sulphur [sic] sulfur-mixed, upon cloth, the latter is passed over calendars heated by steam internally, or run over an iron steam-chest. In either case, if the heat is sufficient, the goods will be but partially vulcanized, and if sent to a tropical climate, will be all stuck together.

The various uses to which caoutchouc has already been and may hereafter be applied, are almost infinite. It has already given tarpaulins and knapsacks, gun-covers and magazines, blankets and pontoons to the army; it will in the future add cartridge cylinders, baggage-covers, and tents. To the navy it has given life-boats, buoys, gun-breechings, caulkings, sheathings, tanks, hose, buckets, and hammock-cloths; it will yet add to these sails, rigging, gun-covers, spring-cables, and cartridge cylinders. In almost every article of external clothing, in carriage-trimmings, harness, roofs, cisterns, furniture, firemen's dresses, book-binding, maps and charts, belting, etc., etc., it is already in constantly growing use.

When caoutchouc is mixed with a large proportion of sulphur [sic] sulfur and undergoes further baking, it becomes ebonite. This substance is of clear and even color, possesses extreme lightness, is a perfect non-conductor, and can be turned by the lathe into any desired shape. It is not corroded by acids or stained by dyes nor shrunken by heat. There is no limit to its use in the manufacture of surgical instruments; and there are no more perfect cutlery handles and trays, bracelets and brooches, chains and crosses, speaking-tubes and astronomical instruments, than are already made from this extraordinary material.

As an insulator for telegraphic wires, caoutchouc has quite put gutta-percha aside. In fact, no submarine cable can be perfect without india-rubber. The demand from this source keeps up the price of the raw material in spite of increasing annual supplies. There are two large American companies and five British companies now at work in Para, obtaining gum for the supply of 1873. Natives are employed in gangs to tap the trees and pour the sap into molds, it having been found more profitable to allow them to pursue their own way than to teach them a more economical course. Curiously enough, and exceptional, too, in regard to general articles of raw material in commerce, the predictions of the more cautious in regard to the supply of caoutchouc have never been realized. It has at no time, in twenty years, exceeded the demand. India-rubber gum has never been a drug in the market. The trees have not been exhausted. Something better has never been found. And the usefulness of the article has never suffered from mistaken enterprise or halting energy. — Hearth and Home.