CHAPTER ELEVEN
RUBBER SHOE MANUFACTURE
Examine the rubbers we wear during the winter and stormy weather.
Rubber shoe coverings are made to protect the shoe from water and snow and may be in the form of either slippers or arctics. The covering is rendered waterproof by means of a compound rubber.
Rubber is the name given to a coagulated milky juice obtained from many different trees, vines, and shrubs that grow on that part of the earth’s surface which forms a band some three or four hundred miles on either side of the equator.
Crude Rubber.
Rubber is graded commercially, according to the district where it is found. In the order of importance it may be divided into three general sorts, viz., American, African, and Asiatic. The best and largest quantities of rubber come from Brazil, along the banks of the Amazon River. The countries in the northern and western part of South America, and the Central American States and Mexico furnish considerable rubber. Eastern and western Africa also produce many kinds of rubber in large quantities, though somewhat inferior to the Brazilian product. The Asiatic rubbers are unimportant in quantity, and, excepting the rubber obtained from cultivated trees in Ceylon, are decidedly inferior in quality.
The fluid rubber obtained from Brazil is called Para and is used principally in the manufacture of rubber footwear. The method of gathering and coagulating the rubber juice (called latex) varies in the different countries. The native first clears a space under a number of trees and proceeds to tap the trees with a short-handled ax, having a small blade, by cutting gashes in the bark. A cup is fixed under each cut to catch the fluid as it flows out. As fast as the cups are filled, they are emptied into a large vessel and carried to the camp to be coagulated. A fire is started in a shallow hole in the ground, and palm nuts, which make a dense smoke, are thrown on. An earthen cover which has a small opening on top is placed over the fire, allowing the smoke to escape through the opening. A wooden paddle is first dipped in clay water and then into the latex and then held over the smoke. The heat coagulates a thin layer of rubber on the paddle. It is dipped again and again in the latex and smoked each time. After being dipped many times, a lump (called biscuit) of rubber is formed. A cut is made in the biscuit and the paddle removed. Then the rubber is ready for market. The world’s crop of rubber in 1911 was about ninety thousand tons.
Few people realize the number of operations necessary to produce from the crude biscuit of India rubber the highly finished rubber shoe of to-day. Briefly stated, the various steps are washing, drying, compounding, calendering, cutting the various parts, making or putting these parts together, varnishing, vulcanizing, and packing. Each of these processes requires a distinct and separate department, and many of these processes are subdivided into minor operations.