57 



So far as the analyses go, the figures are in favour of the planta- 

 tion, and this has found due recognition on the market, where the best 

 dry block, crepe, and other forms have fetched a higher price than 

 hard cure Para, practically in proportion to the percentage of real 

 rubber that these products contain. It may, however, be questioned 

 whether a greater difference in price is not justifiable and will be 

 obtained in favour of plantation rubber when the advantages of a pure 

 and regular product are better recognised and manufacturers have 

 acquired greater experience and confidence in handling it. 



As the best block, crepe, and sheet are washed in a two-roll 

 washing machine immediately after coagulating, and then dried either 

 in the air or in vacuum drying ovens, this treatment on the spot 

 is becoming very general. It seems reasonable to suppose that the 

 manufacturer in this country should be able to take this washed and 

 dried product and use it straight away in his mixing machines with- 

 out any preliminary treatment. On the other hand, all ordinary 

 grades of wild rubber when received by the manufacturer are too 

 impure and contain too much moisture for use right away; they have 

 therefore first to be subjected to a washing process in which the rubber 

 is torn to shreds, in the course of which its " nerve " is affected, and 

 then subsequently to be submitted to a tedious drying process, and if 

 possible storage, in order that the rubber may regain some of the 

 physical properties it has lost on treatment. Not only is it natural to 

 suppose that all this can be avoided by the use of rubber washed and 

 dried on the plantation, but the loss incurred in the washing process 

 is also avoided. This loss in the case of the best wild rubbers, such as 

 hard-cure Para, amounts to from 13 to 17 per cent. 



In order to test the value of plantation grown and plantation 

 prepared rubbers, something more is required than chemical analysis. 

 As for practical purposes it may be said that all rubber is vulcanised 

 in the course of manufacture, and as the properties of vulcanised 

 rubber are very different from the raw article, it appeared to us that 

 the only satisfactory means of determining the value of plantation 

 rubber was to vulcanise it, and carry out physical and chemical tests 

 on the vulcanised product. Moreover, in order to eliminate as far as 

 possible the effect of carrying out such vulcanisation on a laboratory 

 instead of on a manufacturing scale, we made a number of parallel 

 experiments with a sample of typical hard cure Para, which was treated 

 throughout in an exactly similar manner to the plantation rubber. 

 Not only can we test the qualities of plantation rubber in this manner 

 but we are able to put to the test the possibility of mixing and 

 vulcanising washed and dried plantation rubber without any 

 preliminary treatment. 



The hard cure Para was, of course, washed and dried previous to 

 vulcanising, as no results could be got with a product containing 

 moisture. To accomplish this, the wild rubber was cut up, soaked in 

 luke-warm water for some time, and then disintegrated and torn up to 

 shreds in a stream of water, after which it was dried, first in air, and 



