CHAPTER XII. 

 DRYING OF RUBBER. 



General methods — Illustration showing a method of drying biscuit 

 rubber — Presence of water, putrefaction, and surface deposits — 

 Chemicals and artificial heat for drying — Suggestions by Parkin, 

 Burgess, and Weber — Drying in vacuum chambers — Construction 

 of vacuum chambers — High temperatures undesirable — Dickson's 

 drying and coagulating machines — Use of calcium chloride — Advan- 

 tages — Simple rubber-drying sheds for use with calcium chloride — ■ 

 Disadvantages — Experiments in Ceylon , and softening of rubber. 



ON most estates the freshly-coagulated rubber is rolled to drive 

 out as much water as possible, and then either hung up on cords 

 or placed on shelves made of coarse wire netting, coir matting, or wood, 

 and allowed to dry. The rubber cannot be dried in the sun, though 

 a current of warm dry air may be used without any bad effect. The 

 ordinary cacao and tea-drying factories might easily be used for this 

 purpose. The preparation of the rubber in sheets as thin as possible 

 is desirable in order to obtain a dry rubber in the shortest time, 

 though a minimum thickness of one-eighth of an inch is preferred by 

 buyers in Europe. Though the drying process may be hastened 

 by various methods, it is well-known that rubber of good quality 

 can be produced without resorting to any devices for hastening 

 the drying or curing of the product. The illustration on Plate 24, 

 Series A, shows a simple method of drying biscuit rubber as 

 adopted on many rubber estates. Crepe, flake, and lace rubber are 

 capable of being dried more rapidly than thick biscuits or sheets. 



The presence of water in the rubber is often a serious 

 drawback, and the fact that the rubber, if dry, will not undergo putre- 

 factive changes is of sufficient importance to warrant attention to 

 this part of the subject. It should be remembered that when the bis- 

 cuits or sheets are hung up to dry the evaporation of the water is 

 followed by a deposition of the suspended or dissolved impurities on 

 the surface of the rubber, which should be removed. Rapid drying 

 is essential in order to prevent deterioration consequent on oxidation, 

 but too rapid drying is said to induce a softening of the rubber. 

 Chemical and Artificial Heat for Drying. 



Parkin* pointed out that to dry rubber by heat did not seem 

 advisable, and suggested that perhaps quicklime or calcium chloride 

 might be used in the drying chamber. 



* Parkin, I. c. p. 151. 



