RUBBER 66 1 



crepe rubber is subsequently passed once or twice 

 between the smooth even-speed rollers of a sheeting 

 machine. In a large factory, however, it is preferable 

 to have a battery of crepe machines so that the gauge of 

 each is fixed; the fresh coagulum can then be passed a 

 definite number of times through each machine, so that 

 all the rubber gets uniform treatment. 



Worm Rubber. This kind of rubber is now rarely 

 shipped; it usually consists of thick crepe cut into worms 

 by circular knives on a special cutting machine, and 

 subsequently dried in hot-air chambers, such as the 

 " Chula " or " Colombo " driers, or in vacuum chambers. 



Block Rubber. Block rubber consists of crepe rubber, 

 previously cut into worms, artificially dried either in 

 vacuum or hot-air driers, and then blocked under high 

 pressure, say three or four tons per square inch, for several 

 minutes. It is a very convenient form for shipping, and 

 much space and time is saved in its preparation, but we 

 have yet to prove that the rapid method of drying is not 

 deleterious. In any case block rubber is not likely to 

 be superior to ordinary crepe. 



Lower Grades. Till comparatively recently all the 

 lower grades were washed and macerated in an ordinary 

 crepeing machine; this is laborious, and, in the case of 

 bark shavings which are previously soaked for a day or 

 two in water to soften the wood, much of the fine 

 particles of wood, etc., is actually incorporated with the 

 rubber. During the last two years machines in which 

 the rollers revolve under water have been introduced for 

 the preliminary treatment of this material; in these 

 machines the fine particles of wood float on the water 

 and are carried off through wire gauze, and the heavier 

 debris, sand, etc., escapes below. The best and original 

 type of machine of this kind is the Werner-Pfleiderer 

 Universal Washer, of which there are now several 

 smaller local modifications. The chief drawback of this 

 machine is its size and weight and the large amount of 

 power required; it not only produces a much cleaner 

 rubber from bark shavings, but is more rapid, and 

 requires less attention, The rubber from this machine 

 is subsequently creped in an ordinary crepeing" machine. 



Defects in Machinery. All the machines on estates are 



