Gums, Resins, 



470 



[Dec. 1906. 



1. Uniformity. 



2. The eradication, as far as possible, of organic, and the complete removal 

 of inorganic, impurities in the latex. 



3. Acceleration during manufacture to reduce to a minimum exposure 

 to the air. 



4. Small surface exposed after manufacture. 



Rubber manufactured with a view to these principles, besides having the 

 characteristics of a good commercial rubber, will give a system which would appeal 

 to any one who takes an intelligent interest in this industry, and is desirous of 

 establishing a factory organisation on up-to-date principles, and where manual 

 labour will be reduced to a minimum. 



COAGULATING LATEX IN BULK. 



1. Respecting uniformity, the only way to accomplish this is to mix the latex 

 and coagulate in bulk. It has been suggested that the latex from trees of different 

 ages should be kept separate, but this proposition is not one that could easily be 

 carried out in practice. It would be much better to start with the uniform standard ; 

 and if old trees really do give a superior latex, the product of the estate must 

 gradually improve with age. It has not yet been proved conclusively that the older 

 the tree the better the rubber, although there are many indications pointing to this 

 conclusion. 



WASHING THE FRESHLY-COAGULATED LATEX. 



2. The eradication, as far as possible, of organic and the complete removal 

 of inorganic impurities in the latex. The only way to effect this, as everybody who 

 is interested knows, is to wash the freshly-coagulated latex on an ordinary washing 

 machine, such as manufacturers use at home. In fact it is the only practicable 

 method of reducing coagulated latex in bulk to uniformity of size, at the same time 

 thoroughly washing every particle of rubber and removing all mechanical, besides a 

 good deal of the organic, impurities. Tackiness, of which we have heard a good 

 deal lately, and also mildew are a species of micro-organisms, and, although of 

 frequent occurrence in biscuits, seldom if ever oc3ur in properly washed crepe. This 

 is strong testimony to the fact that washing freshly-coagulated latex removes some 

 of the organic impurities which are detrimental to the keeping properties of raw 

 rubber. Whether in addition to this it may be advisable to impregnate the latex 

 with some antiseptic, such as smoke (creosote), formaldehyde, etc., is a matter for 

 further experiment. 



VACUUM DRYING. 



3. Acceleration during manufacture to reduce to a minimum exposure to the 

 air. Despatch during manufacture can only be accomplished by accelerating the 

 drying process, as hitherto this has occupied periods varying from a few days to as 

 many weeks, w r ith exposure all the time to the action of the air. Vacuum drying is 

 the only practicable solution to this, as it combines two very essential points, viz 

 rapidity, without any exposure to the air. By this means it is possible to dry the 

 rubber in two or three hours. Exception has been taken to the use of vacuum 

 dryers, as making rubber sticky, but this is only a matter of temperature which 

 can be regulated mechanically. It is certainly rather a delicate operation and 

 requires a man in charge who thoroughly understands the principles of the machine. 



4. Small surface exposure after manufacture. After removal of the crepe 

 from the vacuum drier it is in a pliable condition in consequence of not being 

 subjected to the hardening influence of air drying (oxidation). In this state it is 

 easily pressed into any conveniently shaped "block," and the whole forms a per- 

 fectly homogeneous mass, hermetically sealed, with a minimum surface exposed, 

 to the air and light. 



