Method of Pressing Rubber into Cakes.
The alum process of coagulation being used.
Several ways were employed in order to coagulate the latex. The simplest was the one used in Matto Grosso. The latex was poured into a rectangular wooden mould, 0·61 m. long (2 ft.), 0·46 m. wide (1½ ft.), and 0·15 m. deep (about 6 in.). Upon the latex was placed a solution of alum and warm water. Then coagulation took place. In order to compress the coagulating latex into solid cakes, a primitive lever arrangement was used—merely a heavy wooden bar, one end of which was inserted into the cavity of a tree, above the wooden mould, while at the other end of the bar heavy logs of wood were suspended. One night was sufficient for the latex to coagulate thoroughly and be properly compressed into cakes, weighing each about 22½ kils. The cakes were lifted out by belts of liane which had been previously laid into the moulds.
The discoverer of the method of coagulating rubber with alum was Henry S. Strauss. He also found that by keeping the latex in hermetically sealed vessels it could be preserved in a liquid state. The same result could be obtained with ammonia.
In the Amazon and Para Provinces a different process was used. The latex was coagulated by placing it near the fire. The heat evaporated the aqueous part and coagulated the vegetable albumen. In order to make what was called a garrafa, or large ball of rubber—some weighed 20, 30, 40 kils. and more—a small ball of latex was made to coagulate round a horizontal bar of wood. That ball was gradually increased in circumference by smearing it over with more latex, which became gradually coagulated and dried by the heat and smoke produced by the burning of certain woods, and of the oily seeds of the urucuri palm, technically known as the Attalea excelsa. In this process the rubber did not remain white, as with the alum process; in fact, it became dark brown, almost black, owing, of course, to the smoke. Locally, the smoking process was said to be the better of the two, for the coagulation with alum took away somewhat from the elasticity of the rubber.
Interesting was the sorveira (Collophora utilis), a tree which gave latex that was quite delicious to drink, but could not be coagulated. The trees, to any untrained person, closely resembled the seringueira, only the leaves were more minute and differently shaped. It must be remembered that nearly all the trees of the Brazilian forest had leaves only at a very great height above the ground, and it was not always easy to see their shape, especially when close to other trees where the foliage got interwoven into an almost solid mass. We frequently enjoyed the sweet milk of the sorveira—it tasted slightly of fresh walnuts with sugar on them. It was unsafe to drink too much of it, as it had injurious effects upon one's digestive organs.
There was there also the leiteiro (or producer of milk), a smaller tree, and the liana macaco, which both produced abundant milk, but in neither case had a way, so far, been found to coagulate it.
The two days spent at Porto Velho were interesting. The four men who had remained with me behaved fairly well, principally owing to the prospect, that, in drifting down stream, they would not have to work, and would be saved the heavy trouble of grooming, packing and unpacking the animals, and the tedious job every morning of riding miles through the country in order to recover those that had strayed away during the night.
"Thank heaven!" exclaimed Antonio, as he gazed at the canoe, "we shall not have to hunt for her every morning!"
