190 



The Supplement to the Tropical Agriculturist 



There were well-known smoked and some pale 

 qualities unquestionably of a higher grade than 

 the average hard-cured Para. A disquieting 

 feature with a few cultivated Hevea sorts was 

 the difficulty experienced when breaking down 

 and masticating them. On the hot mixing rolls 

 some of them did not soften readily, and it was 

 in many cases impossible to obtain a calendered 

 sheet worthy of the name and at all suitable for 

 high-class work. Tough raw rubbers having 

 the appearance of possessing plenty of 'nerve' 

 were not necessarily the best for manufacturing 

 purposes. Having said this about the difficul- 

 ties presented by some Heveas, he proceeded 

 to speak in their favour. There were culti- 

 vated Heveas more amenable on the mixing 

 rolls than hard-cured Para, which calendered 

 as well, vulcanised more rapidly, were stronger, 

 and were just as adaptable as the best native 

 rubber. Plantation rubber, under the right 

 conditions, also got strength from maturity. 

 Oastilloa, Rambong, Landolphia, Funtumia and 

 Guayule rubbers were softer, and compared un- 

 favourably with Hevea. The highett grade 

 Hevea was pre-eminently the rubber from which 

 to manufacture the first coating for cable wires, 

 threads and surgical goods, on account of its 

 reliability, strength and durability under the 

 very severe trials these articles were subjected 

 to. The manufacturer did not find it profitable 

 to use even lower-grade Hevea for these pur- 

 poses. On the other hand, he did utilise Oas- 

 tilloa, Rambong, Landolphia, Funtumia and 

 other rubbers for making tobacco pouches and 

 teats ; but it was doubtful if even the cleverest 

 manufacturer could make a satisfactory hard- 

 wearing pouch from the highly-resinous Guayule 

 rubber without the addition to it of one or other 

 of the former brands. The best pure rubber 

 articles were those made from Hevea. Motor- 

 tyre treads could be made and were manufac- 

 tured successfully from the lower-grade Hevea, 

 Oastilloa and similar brands. This part of the 

 tyre contained a good deal of mineral matter, 

 which increased the tensile strength and aided 

 the tread to resist friction. Moreover, the use 

 of the best Hevea, even allowing for the in- 

 creased strength and durability obtained, would 

 be rather extravagant, as the life of a tyre 

 tread was comparatively short, even when made 

 of the finest material. All classes of raw rubber 

 were used by the solid tyre manufacturer, and 

 it could not be said that if he used the highest- 

 grade Hevea — that was, if the price allowed 

 it — his goods would give greater satisfaction 

 to his customers. Pontinac, when washed, 

 was used without further refining in conjunc- 

 tion with raw rubbers of a higher grade as the 

 base of a compound, which was spread as a 

 solution on to asbestos cloth and paper to be 

 made into steam-packing and so on. 



On Saturday, a general discussion was invited, 

 and Dr. Huber (Brazil) said it would be in- 

 teresting to know the 



OPINION OF MANUFACTURERS ON UNSMOKED PARA 



as compared with wild rubber trees. 



The Chairman — said he could give a partial 

 answer. In his experience it had not been an 

 uncommon thing for manufacturers to get a 

 quantity of third grade— what was called Ser- 

 namby— which they would sometimes rate as 



high as the best Para, and would use for the 

 same purposes ; but it was a product that would 

 vary enormously, sometimes being extremely 

 good and other times extremely bad. He was 

 inclined to think that, at times, scrap rubber 

 which had not been smoked was every bit as 

 good as smoked. 



Dr. Huber — said there were two kinds of 

 scrap exported from Brazil — the real scrap 

 from the trays or pans, aDd that which had 

 coagulated naturally in the tins on the trees. 



Dr. Esh (Germany) — said the experience in 

 Germany was that the best grades of Sernamby 

 would not give the English cat sheet, or be use- 

 ful for goods of high quality. The elasticity 

 after being masticated was very low in com- 

 parison with the real smoked Para. It was also 

 his experience that for hard cured rubber goods 

 — such as motor tyres — they could not use plan- 

 tation rubbers. In some cases Sernamby was 

 better than Para. 



The Chairman— said he knew that at least 

 one of the large manufacturers of tyres used 

 large quantities of plantation rubber, and the 

 tyres had a world-wide reputation for wearing 

 quality. The question of the use of plantation 

 rubber was not a matter of touch and go — not 

 a matter of a single experiment that did not 

 happen to turn out well. He agreed that some 

 kinds of plantation rubber did not resolve so 

 well, milled under the same conditions, as fine 

 Para. That was tempered somewhat by the fact 

 that it was not uncommon to have two classes of 

 plantation rubber — one that masticated well, 

 and one that did not 6eem to stand milling so 

 well, and yet when they were vulcanised one 

 was as good as the other. He had seen that 

 plenty of times. It was impossible to tell by 

 observation how a piece of rubber was going to 

 vulcanise. 



Dr. Esh — said the difficulty with plantation 

 rubber was to get enough of the same kind. One 

 of the biggest German rubber works had said 

 that it was impossible to get English cut sheet 

 from plantation rubber; and that was one of the 

 most important tests. If a rubber would give 

 English cut sheet it was a rubber of fine quality. 

 There were plantation rubbers which stood high 

 mastication; but most of the manufacturers of 

 rubber goods feared there would not be enough 

 of such kinds of plantation rubber. If they 

 bought 10 tons which satisfied them it was diffi- 

 cult to get another 10 tons later of the same 

 quality. At the same time they would be very 

 glad if plantation rubber increased in standard, 

 so as to be thoroughly reliable. 



The Chairman— said it depended a great deal 

 on the methods [of the factory. No [one was 

 more in favour of plantation rubber than he 

 was ; and manufacturers had been able to get 

 along with all grades of rubber of vaying 

 quality, notwithstanding all that was being said 

 about the necessity for uniform plantation 

 rubber. 



Mr. F. Crosbie Roles (Ceylon)— thought the 

 difference in quality was'due to the fact that, 

 in the first instance, old trees were tapped, 

 whereas now young trees were being tapped and 

 young trees did not yield as good latex as the 

 older trees, 



