RUBBER PLANTING 167 



turn to the smoke fumes. When a certain thickness of 

 semi-solid rubber has been obtained, this is scraped out 

 of the cylinder and pressed into a block. Rubber pre- 

 pared in this way contains all the constituents of the 

 latex, including a considerable percentage of water, and 

 may be expected to resemble the Brazilian product 

 closely. The chief point which still requires to be 

 settled is how such rubber will compare in its physical 

 properties with hard-cured Para on the one hand and 

 with the usual forms of plantation rubber on the other 

 hand. Rubber prepared by a somewhat similar method 

 at the Singapore Botanic Gardens has been reported on 

 very favourably by the manufacturers, but one or two 

 experiments are not sufficient to establish the value of 

 the method as compared with other processes already in 

 operation on plantations. 



Blocking. 



Blocks of rubber are prepared in special pres'ses by 

 combining several layers of sheet or crepe rubber, either 

 smoked or unsmoked. Block rubber has the advantage 

 of being very convenient for transport, and is also less 

 liable to undergo damage during transit. From the 

 point of view of the manufacturer, large blocks of rubber 

 possess two disadvantages. It is necessary to cut up the 

 blocks into smaller pieces before the rubber can be 

 further dealt with in the factory. The presence of 

 impurities or adulterations also cannot be detected 



