RUBBER 487 



others. The process is, however, usually accelerated by adding 

 a few drops of acetic* or other acid, the rubber particles thus 

 quickly forming a Moating mass; heating the latex also hastens 

 coagulation. The soft wet rubber is then separated from the re- 

 maining liquid (which is discarded), thoroughly washed by means 

 of water with machine rollers, and then made up into the usual 

 commercial forms, as crepe (Nos. 1 and 2), blanket-crepe, sheet, 

 block, or lace. Until lately it was commonly made into biscuits, 

 but this form is now too laborious to cope with the quantity turned 

 out. Smoked sheet usually commands the highest price at present. 

 Smoking is considered to have a preserving effect on all forms of 

 rubber, and is applied, in the case of wild rubber, by exposing the 

 latex on rollers over the smoke of palm kernels, the roll increasing 

 in layers as fresh latex is poured on, while one man keeps twisting 

 the roll round. Various estates have adopted different methods for 

 treating the latex or rubber with smoke, but smoke-curing on 

 plantations is at present in a transition or experiment stage. 



Drying and Packing. Ordinarily about two months are required 

 for the rubber to become quite dry and ready for packing for 

 export, but with hot-air dryers and light airy drying sheds as are 

 now used drying may be completed in a few days. In packing 

 rubber, it should be laid perfectly flat, not bent or twisted. No 

 packing material should be used with it, and the cases should be 

 planed smooth on the inside. 



RUBBER-PRODUCING TREES, SHRUBS, CLIMBERS, ETC. 



Hevea (Para) Rubber. (Hevea brasiliensis. Euphorbiaceae). 

 A quick growing, tall, erect tree, native of South America, 

 introduced into tropical Asia in 1876, through the Royal Botanic 

 Gardens of Kew, being first established at, and later distributed 

 by, the Botanic Gardens of Ceylon and Singapore. About the 

 year 1898 the cultivation of this and other rubber-producing 

 trees received a great impetus, and has since made rapid strides 

 in Ceylon, Malaya and most other tropical countries. Whereas in 

 1900 the export of rubber from Ceylon was 8,223 lb., of 859 in 

 value, in 1913 it had increased to over 12,300 tons valued at about 

 4,084,600. The area under Hevea rubber at present in Ceylon 

 is estimated approximately at 240,000 acres, and in Malaya at about 

 430,000 acres. Hevea, the most important of all rubber-producing 



* PARKIN* found from experiments that \lo glacial acetic acid to pure latex was sufficient 

 for coagulation, but a somewhat larger percentage is usually allowed by planters. 



