194 THE RUBBER TREE BOOK 



usually again rolled into sheets. While quicker drying is 

 doubtless obtained by such methods, there is more handling of 

 the rubber, and with the sufficiently-rapid methods of drying 

 now in general use the cutting-up of the rubber into small 

 pieces seems unnecessary. 



In some large factories where there is a big output of 

 rubber scrap-rubber, cup-washings, bark- shavings, and some- 

 times even earth-rubber, are in course of treatment eventually 

 massed together, finished off together, and sent out as second 

 or third-grade rubber. Scrap-rubber is the latex which has 

 coagulated on the trees without reaching the latex cups. Cup- 

 washings are the rinsings of the latex cups. Bark-shavings 

 are the fine shavings of bark cut off in the paring away of bark 

 during tapping, and which are, or should be, always carefully 

 collected by the tappers on account of the dried rubber con- 

 tained in them. Earth-rubber is latex which has been spilled 

 on the ground, and is, of course, a very dirty rubber. In treat- 

 ing such low-grade rubber the first endeavour should be always 

 to get rid of as much of the dirt as possible as a preliminary 

 operation and to pick out any stones. 



Where the output of rubber is not very large and there is 

 no " Universal " washing-machine, a good method for getting 

 rid of such objectionable matter is that employed on Bangoen 

 Poerba Estate, belonging to the United Sumatra Rubber 

 Company, Limited. In front of the factory are a number of 

 cement troughs, into which scrap-rubber, bark-shavings and 

 earth-rubber are thrown. A volume of water pours down on 

 the contents of the troughs from overhead pipes, and coolies 

 give the mass a good stirring round. In this way a very large 

 proportion of the dirt is got rid of, and much time and labour 

 are saved when subsequently passing the material through the 

 rollers of the macerator-mill. A strainer at the end of the 

 last trough catches any light fragments of rubber or small 

 pieces of bark swept away by the water. Quite a considerable 

 amount of rubber is saved by this precaution. In the case of 

 the Bangoen Poerba Estate it amounted to 120 Ibs. of dry 

 rubber per month. 



Where there is anything like a large output of rubber a 

 Werner & Pfleiderer " Universal " washing-machine should be 

 installed. The scrap, bark-shavings and earth-rubber should 



