Gums, Resins, 



208 



[Sept. 1906. 



SMOKING PLANTATION RUBBER. 

 By Herbert Wright. 

 In a recent communication to the press, Messrs. Lewis and Peat point out 

 that consignments of biscuits have arrived in London in a heated and sticky- 

 condition, and raise the query as to whether the present mode of preparing biscuits 

 is the best. It is pointed out that Amazon-grown smoke-cured is still the standard, 

 and has for a record of 50 years maintained its reputation for elasticity, strength 

 and durability. One of their advisers is inclined to believe that " Ceylon and Straits 

 biscuits and sheets are at present made too pure, too much moisture being taken 

 out of the rubber, with the result that the elasticity and strength are reduced ; 

 such rubber, it is stated, will not keep, but inevitably becomes soft and treacly 

 if stored for any time or subjected to pressure and a raised temperature." It is 

 finally suggested that the plantation rubber should be smoked and made up into 

 large balls, bottles, or cakes, as in Para. The same firm in their circular, dated 

 December, 1905, state that " the very greatest care should be taken that all rubber 

 is absolutely dry before being packed." Obviously, in the opinion of Messrs. Lewis 

 and Peat, the question of how to prepare the rubber for the market is a vexed 

 one and deserving of much experiment. I have pointed out elsewhere, how Para 

 rubber is smoked in Brazil, and that in addition to the nuts of specified palms and 

 branches of certain tropical trees, certain antiseptic reagents such as creosote, dilute 

 hydrofluoric acid, and corrosive sublimate have been proved to be useful in the 

 preparation of rubber. It has also been shown that rubber prepared from trees 

 30 years old may, if not properly dried become quite as "heated" or "tacky" as 

 that from young trees. If a larger proportion of moisture is left in plantation 

 rubber, I am of the opinion that putrefactive changes will be more apt to occur, 

 and the use of antiseptics either by direct application to the latex or by smoking 

 or coating the rubber will be imperative. In any case, the coating of the rubber 

 particles or smoking the freshly-p re pared rubber biscuits or sheets with any 

 antiseptic is always an advantage as far as the keeping properties of the rubber 

 are concerned; most of the "heating" or "tackiness" in plantation rubber is due 

 to bacteria, which can be prevented from spreading by the use of antiseptics ; if 

 not destroyed they will lead to putrefactive changes in any rubber with which 

 they are brought into contact. Tackiness is really a disease which in unsmoked 

 rubber can be spread by contact, but whether it is more likely to develop on rubber 

 from young or old trees is still a point to be determined. If the consumers will 

 accept the plantation rubber prepared by the use of antiseptics as described, the 

 producers will find no difficulty in meeting their requirements ; in fact several 

 Ceylon estates have, for some time past, sent their rubber to Europe in the smoked 

 condition, but whether better average prices for large quantities have been obtained 

 is not known to the public. A little extra labour and money would be required, and 

 the non-smokers naturally wish to see some promise of better prices before discarding 

 a method of preparation which has hitherto been sufficiently remunerative. 



Whatever the causes predisposing Para plantation rubber to tackiness 

 may be, I certainly believe that the absence of moisture is not one of them ; the 

 necessary bacteria cannot thrive in the absence of water or in the presence of 

 suitable antiseptics. Too rapid drying produces a softening of rubber, but this is 

 a change fundamentally different from tackiness. 



Plantation rubber is never entirely free from moisture, and is not usually 

 dried too rapidly ; it often becomes quite tacky, and for a complete determination 

 of the causes leading to predisposition to this undesirable change it is necessary to 

 take into consideration, in addition to the above, a varied series of factors such 

 as the drying of the rubber in rooms too freely lighted, the imperfect internal and 

 superficial washing of the rubber, the age of the tree or the part from which the 

 latex is obtained, the selection of trees of varying vigour for tapping and the 

 variation in the percentage of objectionable ingredients in latex from trees during 

 certain seasons or from trees tapped injudiciously.— The India Rubber Journal. 



