Plantation Rubber.
Page 3
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The Likelihood of its Wider Commercial Applications.
By Clayton Beadle and Henry P. Stevens.
Ever since its first appearance on the market, the commercial value of plantation rubber as compared with fine hard Para, the accepted standard, has been keenly debated. As a result of the trend of price values and other considerations, the general feeling has been in favour of the wild rubber from the Amazon district. How far this is justified we may leave the reader to judge for himself : we will content ourselves by giving, shortly, some account of considerations bearing on the question, and also the results of our experience in dealing with commercial brands of plantation rubber. Our statements are not confined merely to the views held by manufacturers ind others, but are largely based on our own experience working on a small manufacturing scale. Although much has been written on the question of " nerve," no one has succeeded in giving a terse definition of what is understood by the term. To those not directly engaged in the sale of raw rubbers or the manufacture of rubber goods therefrom, the word " nerve" probably sums up for them the general quality of the unvulcanized rubber. Thus, when the Editor wrote the first leading article for THE COMMERCIAL MOTOR of the 29th July, he stated that plantation rubber does not possess the requisite " nerve" for the manufacture of solid tires, being in this respect greatly inferior to wild rubber, and he probably regards plantation rubber as deficient in resiliency, elasticity, strength and other qualities of rubber par excellence which are posrissed to the highest degree by the wild rubber from the Amazon valley as typified by fine hard Pam. [We took this view after close enquiry.ED.]
It may be as well to remind the reader, at this stage, that fine hard Para and other Para rubbers, such as the soft cures from the same district, are distinguished from wild rubbers of other sources by the process used for the coagulation or curing of the rubber latex. The latex is evaporated in thin layers, one upon another, on a flat wooden instrument resembling a paddle, and the unique characteristic of the process lies in the use of a smoky flame for the source of heat in the operation. Many people attribute special virtues to the smoke, and we are also told that certain varieties of nuts found to hand in the forest are necessary as fuel in order to produce the particular sort of smoke which is most effective. Indeed. earlier writers have been wont to remark on the special providence which has supplied man with the particular indispensable nut in the very place where it was wanted. The feeling in favour of a smoked rubber is even now so strong, that the South-American process is being imitated with more or less success by rubber planters in Ceylon and Malaya. Others, who lay less stress on the smoking process, point to the age of the trees to explain the alleged want of" nerve" of the plantation product. Trees five to eight years old supply most of the plantation rubber, whilst, we are told, the " seringuero " in South America seldom considers it, worth while to tap a tree under 30 years of age. As regards this question, we would point out that on purely botanical grounds no difference would be expected. Whether a tree be five or fifty years old, the latex in both cases is the product of vessels of secondary growth, and is not to be confused with the product obtained from the leaves and twigs where we are dealing with vessels of primary growth. In the second place, as a result of our own work given in a paper re cently read before the Society of Chemical Industry, in which tests upon samples of plantation rubber of ages varying from five to twenty years old were included, we came to the conclusion that the difference in age of the tree was practically without effect on the physical quail ties of the vulcanized rubber, whilst different methods of preparation produced distinct differences in quality. In contrasting the value of plantation rubber with wild rubbers for many purposes, the highest grade of the latter, viz., hard cure Para, is taken as a standard, whereas this grade may seldom—if ever—be used in the goods, and may not he the best suited for the purpose. We need not concern ourselves, here, with a discussion as to the extent that fine hard Para, may or may not be used for solid tires; so much depends on whether we are considering a lightcab tire or a heavy-bus tire, and what we are prepared to pay for the goods. On the other hand, we have no hesitation 'in saying that plantation rubber not only can be, but, has been, used for solid tires of more than one type. We have had before us carefully recorded results of mileage, wear and tear, etc., in contrast with tires. made from wild rubbers. We have worked on different compositions for tire mixings, containing plantation rubber on the one hand, and wild rubbers on the other ; these have been tested in various ways, both in the laboratory and by practical trials on the road. This we can vouch for, although we cannot give further particulars on account of the professional capacity in which we have been engaged when working on these questions.
It must not be forgotten that, although plantation rubber is mostly a high-class product (even the scrap usually fetching a good price), yet there are distinct differences in quality in different brands, and these are brought out when a raw rubber is required for the manufacture of the highest grades of rubber goods, such as cut sheet and elastic thread. In this respect, our experience is that many of the plantation rubbers, although excellent in most respects, have not certain physical qualities termed " tension," or resistance to stretching, to such a high degree as hard cure Para. The differences are not great, but are yet distinct; they probably depend on the method of coagulation of the latex, and the treatment of the raw rubber. This is a question, however, which we cannot go into at length.
Finally, on the question of price, plantation rubbers are fetching less than they did a year ago, in contrast to hard fine Para, but this is largely due to the tightness of the market in this particular grade. The price of hard cure must, for some time at any rate, stand at a higher level than that of plantation rubber, reckoned on the washed and dried rubber, and we offer the following considerations with a view to an explanation of this : (a) " fine hard " is the specified quality in a number of War Office, Admiralty, and other contracts, and must therefore he used for many goods quite apart from the question of merit ; (b) " fine hard is to be had in very large quantities in fairly uniform quality, so that it can be depended on to produce uniform results. whilst plantation rubber is put on the market in almost every imaginable variety of shape. form and quality ; and (e) " plantation rubber " has not yet stood the test of time—if it is to be capable of replacing " fine hard," it must be used by manufacturers who produce the highest class of rubber goods, and these are just the people who will be most cautious, and whose goods are required to last the longest, whether stored or ill Ilse.