662 RUBBER 



adaptations of the washing machines used in the large 

 factories in Europe for washing crude rubbers, but are 

 usually smaller; the chief defects are faulty lubrication 

 methods, whereby oil may come into contact with the 

 rubber, absence of movable guides on rollers, whereby 

 crepe of any desired width could easily be made, and open 

 worm gearing in the front of the machines, which has to 

 be oiled, and with which the rubber may easily come 

 into contact. Machines appear to have been constructed 

 recently with overhead gearing to adjust the back rollers 

 instead of the front, the latter being fixed; this should 

 be a considerable improvement. The receiving trays 

 beneath the rollers should also be narrower than the 

 rollers, otherwise oil from the bearings is liable to drop 

 into them. Copper rollers should be avoided, since, if 

 soluble copper salts are formed, by allowing them to 

 'corrode, the rubber will be seriously and permanently 

 spoilt. 



Drying of Rubber. 



Three methods of drying rubber, apart from smoke- 

 curing, are in general use in the Federated Malay States : 

 (i) Normal air drying; (2) hot-air drying; (3) vacuum 

 drying. 



Methods of drying which involve the condensation of 

 the moisture present in the atmosphere of a drying room 

 by refrigeration processes have not so far been adopted. 



Normal Air Drying. At the present time the natural 

 air drying of rubber in the case of thin crepe appears to 

 be generally quite satisfactory, and only occupies from 

 four or five to about ten days, depending on the thick- 

 ness and even finish of the rubber. The best estate drying 

 rooms consist of a two-story building in which the No. I 

 crepe is hung on racks in the upper story; the ceiling of 

 the bottom story, which constitutes the floor of the top 

 story, is constructed of open broties or strips of wood, 

 at any rate under the racks in the top story, leaving only 

 sufficient passage room between each set of racks; venti- 

 lation is improved by means of a jack-roof or ventilating 

 shafts. The drying sheds are usually built of corrugated 

 iron, and, unless they have a high roof, the latter should 



