465 



These bubbles and blow holes do sometimes occur after vulcanisa- 

 tion, and care has always to be exercised to prevent their occurrence 

 and anything which might lead to their formation has to be care- 

 fully avoided. Whether this objection to the use of a volatile acid 

 in curing the rubber is really sound, can only be decided by practical 

 experience in working with rubbers so cured, but the objection is 

 actually held, and the fear entertained, by some of the most pro- 

 minent of the rubber manufacturers in England, and the knowledge 

 of the fact that acids have been used in the curing of plantation 

 rubber makes the manufacturer less inclined to use crepe or plan- 

 tation washed rubber without a further re-washing in the factorv. 

 Another objection to the use of acid preservative, and the addition 

 of any drug at all to the latex, lies in the possible action of such 

 drug on the rubber itself. Speaking a priori and considering the 

 mild chemical character of acetic acid, and the preservative action 

 of formalin, together with the singularly inert nature of rubber, 

 I should not expect any harmful action whatever to occur. I have, 

 however, seen samples of rubber made from latex to which small 

 amounts of various aniline dyes had been added. Some of the dyes 

 (the reds especially) had produced most marked effect, making the 

 rubber hard and brittle, and as readily torn as thick paper. Other 

 dyes appeared to have had little deleterious effects. This perishing 

 of the rubber had certainly been brought about by the action of 

 quite trifling amounts of what are regarded as harmless and inactive 

 chemicals. I have already mentioned cases of plantation rubber 

 perishing utterly in a few years from unknown causes. With these 

 instances before me I feel less inclined to treat the possibility of 

 acetic acid or formalin causing rubber to perish as absurd or 

 fanciful, and until the question has been experimentally investigated 

 I should recommend that, wherever possible; the use of any 

 chemical w hatever be avoided. The position is therefore this — 

 some of the users of rubber object to the rubber being cured with 

 acid, and in the absence of experimental evidence we are not 

 justified in assuming acids, even vegetable ones such as acetic, to 

 be harmless. To avoid using any coagulant is only practically 

 possible where a mechanical treatment of the rubber by a washing 

 machine is in use, and then it is a matter for consideration whether 

 the use of acid, which has been extremely convenient in assisting 

 and controlling coagulation, should be discontinued from fear that 

 such use will produce a rubber which will not stand the test of 

 time, and which will perhaps injure in the future the reputation of 

 plantation grown and cured rubber. 



DRYING RUBBER. 



15 Until the introduction of mechanical washing of coagulated 

 rubber and the formation of crepe, drying had been a troublesome 

 operation in the preparation of rubber for export. Artificial heat 

 almost always led to the softening of the rubber, and often through 

 inefficient control of the temperature caused it to become distinctly 

 tacky. Crepe rubber dries easily and well if simply hung up in a 

 dark but airy shed, and the preparation of rubber in this form 



