654 RUBBER 



on curing in a similar way, whereas it is now necessary 

 to carry out preliminary experiments with different 

 batches, which the smaller manufacturers, in the absence 

 of a testing laboratory or scientific advice, are not in a 

 position to do. If it is found impossible to obtain 

 absolute uniformity, as well as superior rubber, from all 

 estates, from " first quality " latex, samples must be 

 tested, graded, and shipped with guarantees or certificates 

 of quality, showing the rate of cure at which the best 

 result is obtained in subsequent tests for elasticity, 

 resiliency, and strength, in order to enable the manu- 

 facturer or his agent to purchase according to his require- 

 ments. In the absence of such certificates, uniformity is 

 relatively of more importance than actual quality, owing 

 to the absence of a satisfactory method of purchase. 



Until the various testing stations which have recently 

 been inaugurated at the Agricultural Department in the 

 Federated Malay States, at the Imperial Institute in 

 London on behalf of Ceylon, and the slightly older 

 station at the Technical High School, Delft, together 

 with the Department of Rubber Testing at the Koniglich 

 Materialprufungsamt in Gro'sse-Lichterfelde, Berlin, have 

 been at work for some time, the lines along which work 

 must be carried out in the country of origin of the rubber 

 will be the standardization of rubber on different estates, 

 in so far as uniform methods of coagulation, machining, 

 and curing may be adopted. Thus in the case, e.g., of 

 smoked sheets, it would be well if all estates were to 

 coagulate a latex of a standard density reduced by the 

 addition of water under control in the factory where 

 necessary, so that equal volumes of the latex would 

 always yield the same weight of dry rubber; such rubber 

 should be uniform in character. It is impossible to 

 produce satisfactory sheet rubber by the coagulation of 

 pure concentrated latex with acid coagulants of, say, 

 i per cent, or 5 per cent, strength, owing to various 

 defects produced in the rubber from comparatively thick 

 latex, so that in the case of pure latex it has to be diluted, 

 or what amounts to the same thing, a large quantity of 

 a more dilute acid coagulant must be added. 



I have found that a very satisfactory sheet can be made 



