Makers of Many Things

by Eva March Tappan

When the rubber juice reaches the camp, it is poured into a great bowl. The men build a fire of sticks, and always add a great many palm nuts, which are oily and make a good deal of smoke. Over the fire they place an earthen jar shaped like a cone, but without top or bottom. Now work begins. It is fortunate that it can be done in the open air, and that the man can sit on the windward side, for the smoke rises through the smaller hole thick and black and suffocating. The man takes a stick shaped like a paddle, dips it into the bowl, and holds it in the smoke and heat, turning it rapidly over and over till the water is nearly dried out of the rubber and it is no longer milky, but dark-colored. Then he dips this paddle in again and again. It grows heavier at each dipping, but he keeps on till he has five or six pounds of rubber. With a wet knife he cuts this off, making what are called "biscuits." After many years of this sort of work, some one found that by resting one end of a pole in a crotched stick and holding the other in his hand, a man could make a much larger biscuit.

For a long time people thought that rubber trees could not be cultivated. One difficulty in taking them away from their original home to plant is that the seeds are so rich in oil as to become rancid unusually soon. At length, however, a consignment of them was packed in openwork baskets between layers of dried wild banana leaves and slung up on deck

in openwork crates so as to have plenty of air. By this means seven thousand healthy little plants were soon growing in England, and from there were carried to Ceylon and the East.

On the rubber plantations collecting juice from trees standing near together and in open ground is an altogether different matter from cutting a narrow path and forcing one's way through a South American or African jungle. The bark of the trees is cut in herringbone fashion. The collector simply slices a thin piece off the bark and at once milk begins to ooze out.

On the great plantations of the East the rubber is collected chiefly by Chinese and Indians. They are carefully taught just how to tap the trees. They begin four or five feet from the ground, and work down, cutting the thinnest possible slice at each visit. When they have almost reached the ground, they begin on the opposite side of the trunk; and by the time they have reached the ground on that side the bark on the first side has renewed itself. The latex is strained and mixed with some acid, usually acetic, in order to coagulate or thicken it. It is then run between rollers, hung in a drying house, and generally in a smokehouse.

The rubber arrives at the factory in bales or cases. First of all it must be thoroughly washed in order to get rid of sand or bits of leaves and wood. A machine called a "washer" does this work. It forces the rubber between grooved rolls which break it up; and as this is done under a spray of water, the

rubber is much cleaner when it comes out. Another machine makes it still cleaner and forms it into long sheets about two feet wide.

Having thoroughly wet the rubber, the next step is to dry it thoroughly. The old way was to hang it up for several weeks. The new way is to cut it into strips, lay it upon steel trays, and place it in a vacuum dryer. This is kept hot, and whatever moisture is in the rubber is either evaporated or sucked out by a vacuum pump. It now passes through another machine much like the washer, and is formed into sheets. The square threads from which elastic webbing is made may be cut from these sheets, though sometimes the sheet is wound on an iron drum, vulcanized by being put into hot water, lightly varnished with shellac to stiffen it, then wound on a wooden cylinder, and cut into square threads. Boiling these in caustic soda removes the shellac. To make round threads, softened rubber is forced through a die. Rubber bands are made by cementing a sheet of rubber into a tube and then cutting them off at whatever width may be desired. Toy balloons are made of such rubber. Two pieces are stamped out and joined by a particularly noisy machine, and then the balloon is blown out by compressed air.

Early in the nineteenth century it was known that rubber would keep out water, but it was sticky and unmanageable. After a while a Scotch chemist named McIntosh succeeded in dissolving rubber in naphtha and spreading it between two thicknesses of

cloth. That is why his name is given to raincoats made in this way. Overshoes, too, were made of pure rubber poured over clay lasts which were broken after the rubber had dried. These overshoes were waterproof,—there was no denying that; but they were heavy and clumsy and shapeless. When they were taken off, they did not stand up, but promptly fell over. In hot weather they became so sticky that they had to be kept in the cellar; and in winter they became stiff and inelastic, but they never wore out. How to get rid of the undesirable qualities and not lose the desirable ones was the question. It was found out that if sulphur was mixed with rubber, the disagreeable stickiness would vanish; but the rubbers continued to melt and to freeze by turns until an American named Charles Goodyear discovered that if rubber mixed with sulphur was exposed to about 300° F. of heat for a number of hours, the rubber would remain elastic, but would not be sticky and would no longer be affected by heat or cold. This is why you often see the name Goodyear on the bottom of rubbers.