^94 RUBBER 



instance, in the Shevaroy Hills during 1912 an average 

 of 5,400 three-year-old trees tapped five times at weekly 

 intervals gave a total yield of 142 J Ib. of dry rubber, and 

 during a three months' tapping season an average of 5,000 

 such trees gave a total yield of 3,280 Ib. of dry rubber, 

 or a yield of about 130 Ib. per acre. 



In Coorg 19,260 six-year-old trees, tapped on an 

 average of forty times each, gave 7,486^ Ib. of dry 

 rubber, or a little over f Ib. per tree. This represented 

 170 acres with about 115 tappable trees per acre, but 

 another 40 per cent, per acre have yet to arrive at the 

 tapping stage. 



The method of preparation of rubber from the latex is 

 extremely simple. The usual coagulant is acetic acid. 

 As a result of experiments conducted in Coorg, however, 

 it would appear that if a coagulant is used at all, a 6 per 

 cent, solution of formic acid at a temperature of 80 F. 

 gives the best results, producing a rubber which when 

 dry is very elastic and strong. 



The system adopted now, however, is not to use any 

 acid or chemical coagulant at all, but to simply allow 

 the latex to coagulate slowly in hot water in a dark 

 room. After coagulation it is rolled and thoroughly 

 washed to remove resins, this rolling and washing being 

 done by machinery. It is then dried in hot air in a dark 

 room, and finally made into sheet or crepe, as the case 

 may be, in the ordinary way. Some smoked sheet has 

 been prepared and high prices obtained for it, but 

 methods of smoking are at present in an experimental 

 stage. 



Ceara rubber contains more resin than Hevea, and it 

 is difficult to remove all of this by washing and rolling 

 without detracting from the physical qualities of the 

 rubber; but as the trees get older this defect will probably 

 largely disappear. In quality, the rubber when made into 

 biscuit or sheet is quite equal to the best plantation Para, 

 and it commands almost as good a price. 



There is much diversity in the yield of trees produced 

 under similar conditions and even growing side by side, 

 and with the object of eliminating this variable factor as 

 far as possible, and at the same time increasing the yield 



