138 



Saps and Exudation*- 



bulk which results in the production of crepe rubber. Although at present neither 

 clean biscuit, sheet, worm, nor crepe rubber need be washed for ordinary use, yet if 

 washing and sheeting plantation rubber is to be dispensed with in the manufactory, 

 it would be a great advantage when dealing with the larger quantities to have it 

 ready in the washed and sheeted form, and the advantage of crepe over other forms 

 would be most marked when dealing with many tons at a time. t 



ADULTERATION OF WASHED RUBBER. 



8. There is one danger connected with the use of a washing machine on a 

 plantation. By its means adulteration with inferior rubber, rubber substitutes, 

 and recovered rubber, could be carried out without possible detection by eye or 

 and inspection, although chemical analysis or practical use of the rubber would, 

 reveal the sophistication. In unprincipled and fraudulent hands such adulteration 

 might be carried to a considerable pitch before detection occurred, and this possi- 

 bility of misuse should not be lost sight of by those who are responsible for the purity 

 of the rubber produced, 



ANALYSIS OP RUBBER. 



9. The chemical composition of rubber has no consideration either from the 

 buyers or the manufacturers— the former base their valuation entirely upon the 

 appeai'ance, feel, smell, and apparent strength of the rubber when pulled about in 

 their hands, the latter rely chiefly upon the way the rubber works upon their 

 machines during manufacture, though in a few instances properly controlled and 

 systematically carried out tests of tensile strength and elasticity are made with 

 samples of the rubber prepared and vulcanised. The percentage amount of the 

 impurity which is inherent in the rubber, and which cannot be removed by washing 

 — that is, the oily, resinous, and nitrogenous, or proteid, impurity — is practically 

 never determined in the factory, and a statement of these values with the rubber 

 for sale would neither be understood nor attended to. In the present state of 

 ignorance as to the influence of these ingredients upon the working qualities of the 

 rubber during manufacture, the apathy with which variations in their amounts in 

 the raw material are regarded is natural and quite intelligible. 



PACKING. 



10. There are several points which must be remembered in packing rubber 

 Rubber at temperatures above 65°F. is naturally adhesive, and clean surfaces 

 pressed into contact tend to stick to one another, though the rubber be dry and 

 show no vestige of tackiness. Rubber during transit invariably shrinks in bulk 

 owing chiefly to the action of its own weight in compacting the mass, and partly 

 perhaps to a natural shrinkage of the rubber substance with the ageing of the 

 rubber. Dust and grit which find way inside the cases adhere to the rubber, 

 The care requisite in packing, therefore, depends upon the form in which 

 the rubber is shipped. If in clean washed crepe, which it is hoped will be used 

 without further washing and sheeting, every care should be taken to prevent the 

 layers adhering to one another, aud to a void the use of any packing material which 

 can make a dust out of itself, or which will admit dust and grit from outside. This 

 can be effected by the use of clean, well m tde and fitted cases, which should not 

 contain more than 80-100 lbs., of rubber, and which might with advantage be parti- 

 tioned to prevent the whole of the rubber resting with full weight upon itself. No 

 inuer lining of common paper or other friable material should be used—such wrap- 

 ping is bound to get broken in transport, and particles of it work their way between 

 the layers of rubber, and obstinately adhere to the rubber. The first shipment of 

 crepe rubber which I saw unpacked had been in wooden cases with paper lining. 

 When the folds of separate layers of rubber were pulled apart, a shower of fine grit 

 particles of paper, and dust, was then thrown out from the rubbei. This rubber 



