[Ill.u.s.tration: A PLANTATION IN BORNEO

_Courtesy of the B. F. Goodrich Co._]

How is Rubber Smoked?

After the juice has been gathered in this way, the native builds a fire; over it he places a cover shaped like a large bottle with the bottom knocked out of it. This fire is built of oily nuts found in the forest, and the thick smoke arises through what would be the neck of the bottle.

[Ill.u.s.tration: SMOKING RUBBER ON THE LOWER AMAZON

_Courtesy of the United States Rubber Co._]

With a stick shaped something like the wooden shovels used at the seash.o.r.e, he dipped into the milky juice in the bowl, then turned this stick or paddle around very rapidly in the smoke until the juice baked on the paddle. He then added more juice and went through the same operation again and again until there were between five and six pounds of rubber baked on this paddle. He then cuts this off with a wet knife which made it cut more rapidly. That formed what is called a rubber "biscuit," and he then started over again for his next five or six pounds. Later, as the demand for these "biscuits" increased, instead of the native using the paddle, he erected two short fence-like affairs about six feet apart, but parallel with each other, and in between was the smoky fire. Then he obtained a long pole, stretched it across these two rails and poured a small quant.i.ty of this juice on this pole, over where the smoke came in contact with it, and rolled the pole around until this juice was baked, adding more, until, instead of a small five- or six-pound "biscuit," he would get an immense ball. In order to get this off his pole, he would jog one end of the pole on the ground until the "biscuit" would slide off. This is the way crude rubber first came into our market and the way it comes today.

[Ill.u.s.tration: SMOKING RUBBER--UPPER AMAZON

_Courtesy of the United States Rubber Co._]

How was Vulcanizing Discovered?

Up to this time, these "biscuits," when exposed to heat, would become very soft and sticky, and when exposed to the cold, would become hard like a stone.

[Ill.u.s.tration: REMOVING BISCUIT FROM POLE AFTER SMOKING

_Courtesy of the United States Rubber Co._]

There was an American by the name of Charles Goodyear who had heard how the natives of the rubber-growing countries used this milky juice in many ways for their own benefit. One use they put it to was the waterproofing of their cloaks. How could this be done so that our clothing would be made water-tight and yet not be sticky in summer or stiff in winter? Goodyear devoted a great deal of his time to solving this problem, and, like many other great inventors, he pa.s.sed through many trials. His many failures caused his friends to forsake him and he was put in prison for not paying his debts. He persisted in his quest, however, and it was accident at last that opened the way to discovery of the processes of vulcanization for which Goodyear was seeking.

[Ill.u.s.tration: INDIAN WATERPROOFING CLOTH BY "PAINTING" IT WITH RUBBER "MILK"--BRAZIL

_Courtesy of the United States Rubber Co._]

At Woburn, Ma.s.s., one day, in the spring of 1839, he was standing with his brother and several other persons near a very hot stove. He held in his hand a ma.s.s of his compound of sulphur and gum, upon which he was expatiating in his usual vehement manner, the company exhibiting the indifference to which he was accustomed. In the crisis of his argument he made a violent gesture, bringing the ma.s.s in contact with the stove, which was hot enough to melt India-rubber instantly; upon looking at it a moment afterwards, he perceived that his compound had not melted in the least degree! It had charred as leather chars, but no part of the surface had dissolved. There was not a sticky place upon it. To say that he was astonished at this would but faintly express his ecstasy of amazement. The result was absolutely new to all experience--India-rubber not melting in contact with red-hot iron! He felt as Columbus felt when he saw the land bird alighting upon his ship and the driftwood floating by. In a few years more his labors were crowned with success.

This great invention made it possible for us to have rubber boots and rubber shoes and many other things made of rubber.

[Ill.u.s.tration: _Courtesy of the United States Rubber Co._]

Up to this time, all the rubber was called Para rubber, named from the town of Para in Brazil, from which all rubber was shipped. The full-grown tree is quite large, ranging sixty feet and over in height and about eight feet around the trunk. It has a flower of pale green color and its fruit is a capsule containing three small brown seeds, with patches of black. These seeds lose their life very quickly, so a great deal of care is necessary to pack them if they are wanted to plant in another place. The safest way is to lay them loosely in a box of dry soil or charcoal.

[Ill.u.s.tration: RUBBER TWIGS

_Courtesy of the United States Rubber Co._]

The rubber tree grows best in rich, damp soil and in countries where the temperature is eighty-nine to ninety-four degrees at noon-time and not less than seventy-four degrees at night, and where there is a rainy season for about six months in the year, and the soil and atmosphere is damp the year round.

The name of this species of tree is Hevea, but many years ago it was called Siphonia on account of the Omaqua Indians using squirts made of a piece of pipe stuck into a hollow ball of rubber.

How did Rubber Growing Spread to Other Places?

Back in the seventies an English botanist, Wickham by name, smuggled many Hevea seeds out of Brazil. The tree was found to grow well in the Eastern tropics and today the rubber plantations of Ceylon, Borneo, the Malay Peninsula and neighboring regions are producing more than half of the world's supply of crude rubber. Here the natives work under pleasant climatic conditions and the trees under cultivation grow better and yield better than in the forest.

On these plantations, rubber trees are cultivated just the same as other crops. All weeds are removed and great care is used with the young trees. Low-growing plants which absorb nitrogen from the air which enriches the soil, such as the pa.s.sion flower and other sensitive plants, were planted around these small rubber trees, for it was found that when the weeds were removed to give the trees a chance to grow, the ground became hard and dry.

[Ill.u.s.tration: _Courtesy of the United States Rubber Co._]

The method of tapping is different, too. Instead of ten to thirty taps, a series of cuts the shape of a V is made on four sides of the tree, from the bottom up to as high as a man can reach, and a cup placed at the point of the V. Another way is to make one long cut down the tree and then cut out slanting channels about one foot apart into this, and put a cup at the bottom of the long cut; another is making a spiral around the tree with the cup at the bottom.

How is Rubber Cured on Modern Plantations?

With these big plantations some other way to cure the rubber had to be devised from the smoking process used in curing the native rubber which comes from South America. The milky juice is emptied from the cups into a tank and lime juice is added and it is then allowed to stand. The juice, as it comes from the tree, contains considerable water: the lime juice is added to separate the rubber from the water.

[Ill.u.s.tration: A YOUNG RUBBER PLANTATION

_Courtesy of the United States Rubber Co._]

Sometimes separators are used much like our cream separators; in fact, the whole process and the appearance of the interior of these rubber "dairies" very much resembles our own dairies where real milk is made into b.u.t.ter, curds or cheese.

Para, at the mouth of the Amazon, and Manaos, a thousand miles up, are both modern cities of more than one hundred thousand population. They have schools, churches, parks, gardens and museums, and, except for the Indians, certain peculiarities in architecture and the ever-present odor of rubber, they differ but little from our northern cities of equal size. Here the rubber markets are located and here the rubber is carefully examined, graded, boxed and shipped to New York or Liverpool.

Plantation rubber usually comes in the form of sheets of various shapes and sizes. The rubber shown here is in oblong sheets. Sometimes it is in the form of "pancakes" or in "blocks." Often, after being coagulated, it is smoked, and "smoked plantation sheet" is, next to Para, the best rubber obtainable.

[Ill.u.s.tration: _Courtesy of the United States Rubber Co._]

How is Crude Rubber Received Here?

Crude rubber is received in many forms under various names. There are more than three hundred standard kinds, depending on source and method of handling; _e. g._, "Sernamby" is simply bundles of Para tree sc.r.a.p and sc.r.a.p from the cups where milk has cured in the open air. "Guayule"

is a resinous rubber secured from a two-foot shrub that grows on the arid plains of Texas and Northern Mexico.

Our picture shows a bin of crude up-river Para the finest rubber known.

Every "biscuit" or "ham" has been cut in two to find out whether the native has loaded it in any way.

[Ill.u.s.tration: ANOTHER CEYLON TAPPING METHOD--THE HERRINGBONE

_Courtesy of the United States Rubber Co._]

How is Rubber Prepared for Use?

Now that we have rubber so that it can be used, we find there are a great many operations necessary between gathering the crude rubber and finally the finished rubber coat or shoe. These various operations are called washing, drying, compounding, calendering, cutting, making, varnishing, vulcanizing and packing and each one of these main operations requires several smaller operations.

The grinding and calendering department is the one in which the crude rubber is washed, dried, compounded and run into sheets ready to be cut into the various pieces which const.i.tute a boot or shoe.

[Ill.u.s.tration: RUBBER MARKET IN MANAOS