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 constitute a boot or shoe. The cultivated rubber comes practically clean, but the crude rubber "biscuits" contain more or less dirt and foreign vegetable matter which have to be removed. The rubber is softened in hot water for a number of hours and then passed through the corrugated rolls of a wash mill in which a stream of water plays on the rubber as it is thoroughly masticated and formed into thin sheets. These sheets are taken to the drying loft. Here they are hung up so that the warm air can readily circulate through them and are allowed to remain from six to eight weeks, until every trace of moisture has been removed. The vacuum dryer is used where rubber is wanted dry in a short space of time. This is a large oven containing shelves. The wet sheets of rubber are cut in square pieces, placed on perforated tin pans and loaded into the dryer, which will hold about eight hundred pounds of rubber. The

Another Ceylon Tapping Method - The Herringbone.

Courtesy of the United States Rubber Co.

Rubber Market in Manaos.

Courtesy of the B. F. Goodrich Co.

Courtesy of the United States Rubber Co. SPECIAL DESIGNED MACHINE FOR CUTTING RUBBER.

Tapping Hevea Rubber Tree on Ceylon Plantation.

Courtesy of the United States Rubber Co.

doors are closed, fastened, and by the vacuum process the water is extracted, leaving the rubber perfectly dry in about three hours' time.

After the rubber is dry, and has been tested by the chemist, it goes to the grinding mills where it is refined on warm rolls and made ready for the compounding or mixing. It is impossible to make out of rubber alone, shoes or other products that will withstand extreme changes in temperature; certain amounts of sulphur, litharge and other ingredients are necessary in combination with the pure rubber to give a satisfactory material. The gum from the grinding mills is taken to the mixing mills, where, between the large rolls, the various materials are compounded into a homogeneous mass. The compounded rubber goes from the mixing mills to refining mills, to be prepared for the calenders.

Softening Vats.

Courtesy of the B. F. Goodrich Co.

Courtesy of the United States Rubber Co..

Automobile, motorcycle and bicycle tires, belting, footwear and many other rubber articles must have a base or backbone of cotton fabric, and in order that the fabric may unite firmly with the rubber it must be "frictioned" or forced full of rubber. This is done by drawing it between enormous iron rollers, rubber being applied on its surface as it passes through. The pressure is so great that every opening between the fibers of cotton, every space between threads is forced full of rubber.

The fabric is then ready to go with the milled rubber to the various departments of the factory to be incorporated into rubber goods. The calender is also used to press rubber into sheets of uniform thickness.

The Mill Room.

Courtesy of the B. F. Goodrich Co.