The huge stock of Para rubber, that is rubber obtained from the Amazon section, to be found in any of the leading rubber factories counts well up into the thousands of dollars. With rubber at or near $1.50 per pound, a stock of ten to fifty tons runs up into the five or six figures.
This crude rubber, as it comes from the Amazon, contains more or less dirt, pebbles, and other foreign substances, which must be removed.
The large cakes of crude rubber are first broken up by a cracker machine, consisting of two large, revolving steel cylinders, from which the product falls into pans or trays. It goes then to a machine known as a “washer” or “sheeter,” where it is run between revolving cylinders, upon which a continuous spray of clean water is maintained. After being rolled into rough sheets, it is put into a tank, from which it is taken to the “beater” machine, in which water runs continuously, and then it is washed again and “sheeted out.” It is then dried in one of two ways.
(1) The older way. The sheets are hung over rods in a large room, and allowed to dry in the air. To facilitate the same, a fan or blower is often used to cause a circulation and removal of the moisture-laden air. This requires a period of from one to two or three months.
Washing and Drying.
(2) The second method is called vacuum drying. This process is gradually being introduced, so that now probably more rubber is dried in vacuum than by air. The vacuum drier consists of a large iron cylinder filled with plates, through which steam is allowed to circulate. The rubber is placed on the plates and the air is exhausted from the cylinder by means of an air pump until very nearly twenty-six degrees of vacuum are obtained. By this process only from two to three hours are required to produce perfectly dry rubber.
The making of a rubber shoe is not the simple matter which might at first be supposed. An ordinary rubber shoe consists of at least seven or eight different parts, sometimes twenty-one parts to a pair, while a high-button gaiter has seventeen distinct parts, and a rubber boot has twenty-three different pieces. There are insoles, outsoles, stays, piping, foxing, and a dozen other different pieces, each one of which is necessary to the proper construction of a rubber shoe or boot. The thinner sheets for the uppers are cut by hand, the deft work of the cutters in following the patterns outlined on the sheets being the result of years of practice. The sheets of rubber from which the uppers and soles are cut are at this stage of the work plastic and very sticky. It is necessary on this account to cut the various pieces one by one, and keep them separate. The soles and some of the heavier pieces are dried out by the machine, and the heels are made by a special machine, but by far the greater part is done by wonderfully skilled hands. All of these parts which go to make a shoe, or the twenty-three parts which go into a boot, are collected and sent to the making department, which, in most factories, is a large room containing several hundred operatives, each working by herself, and bringing the many separate parts into the fully finished footwear.
Calender Room.