The Preparation of Plantation Rubber

by Sidney Morgan

(2) In the majority of specimens upon which had been smeared a small streak of lubricant taken from the bearings of machines, tackiness had supervened, and had developed likewise in the contact “blanks.”

(3) In all cases where a trace of copper salt had been used to adulterate the fresh lubricant, tackiness was to be noted in the course of a short period (a week upwards) after the rubber was dry. Development was slow, but progressive, over the full period of experiment, and the “blanks” in contact were affected. The degree of affection was determined by the proportion of copper salt employed. In the worst cases the affected strip of rubber had deteriorated and disintegrated to such a degree as to cause a distinct longitudinal gap, the edges of which appeared to consist of a moist gummy substance of a deep syrup colour. The adjacent blanks in some cases exhibited a similar appearance in lesser degree, or were merely affected by a characteristic brownish stain.

These observations regarding the possibility of damage to crepe rubbers from the existence of brass “liners” or “bushes” in the bearings of the machines lead to the natural query as to whether the use of brass is necessary. Experience shows that it is not necessary. Machines in use for years have been running with plain bearings of iron or other metallic substances. Satisfaction is obtained without the use of brass.

Cotton and other Fibre.—One of the most frequent complaints made against low grade crepes is the presence of fibre—generally classed in a wholesale fashion as “cotton-waste.”

It is true that some years ago most of the complaints were genuine in referring the cause to cotton-waste. The defect arose chiefly owing to the careless use of this material in the factory. Lumps of waste when discarded were often thrown to the ground, and became mixed with the heaps of scrap rubber and bark-shavings awaiting attention. The fault was one of sheer negligence, and nothing can be advanced in extenuation. Even when the soiled waste was thrown into the external drains, it often returned to the factory mixed up with the scraps of rubber recovered by means of the drain-screens.

As far as the complaint concerns itself with cotton-waste only, the remedy is plain, and lies in the power of the management by reason of the ability to restrict the use of “waste” only to the engine-drivers and mechanics.

In the vast majority of cases, however, the defect arises from circumstances beyond the direct control of the factory, and under conditions which make it difficult to check the evil. Although against instructions, and for the purpose of fulfilling other orders, some coolies persist in using pieces of cloth for cleaning cups. In course of time, unless the practice is detected, this cloth becomes coated with rubber. Careless coolies throw it away, when it may be collected by the individuals who gather earth-scrap; or it may be brought into the factory in the tappers’ scrap-bag.

Cases have been known in which the fibrous matter observed in the dry crepe rubber was of such a nature as to indicate that the source might be attributed to leaf-stalks which had passed through the scrap-washer. It is an easy matter to condemn the sorting as being careless, but it is another matter to instil into the mind of factory coolies such a respect for easy and sane precautions that the practice of them will be continued when the eye of the supervisor is not fixed upon the workers.

It will be clear that contamination by fibrous matter should be limited practically to the lowest grades of rubber.

The appearance of cotton-waste in high-grade crepes must be most unusual, and the writers have not yet seen a case in a drying-house. That it does occur, however, seems to be evident from brokers’ reports. It is extremely difficult to imagine how the waste enters the rubber. One possible explanation is that a coolie may have been cleaning the rolls surreptitiously with waste, which may have passed later into the rolls together with rubber. Another explanation was offered in one factory by the observed fact that coolies engaged in cutting up coagulum, ready for passing into the machines, kept a wad of waste for the purpose of keeping the knife-blade clean. This may have found its way into the rolls. It must be recorded that in the course of many years of experience no case has been seen in any drying-house of contamination of the higher grades of crepe by fibrous matter.