PARA-RUBBER CULTIVATION 603 



piece of opaque white rubber, which on drying turns to a 

 lightly coloured translucent biscuit. 



Biscuits prepared in some such fashion are still made on the 

 smaller properties, as no machinery is required, but on large 

 estates more economical wa}'s of procedure have been devised. 



Coagulation can be brought about much more speedily by 

 the use of a rotating machine, known as a coagulator, and 

 acting after the manner of a churn. The latex with the requisite 

 amount of acid is poured into the coagulator, and after a few 

 minutes' rotation the clots are formed. These are then passed 

 through a washing mill. Water plays on the rubber, as it is 

 masticated and stretched in its passage through the corrugated 

 rollers, clearing out the acid and impurities generally. The 

 rubber finally emerges in a continuous broad ribbon, re- 

 sembling crepe in texture, which is readily dried. If smooth 

 rollers be used then " sheet " rubber is made. Sometimes the 

 clots are cut up by a special machine into small pieces, and 

 such rubber is known as "worms." 



Caoutchouc prepared in these different forms is not fit 

 for shipment till it is dry, i.e. until the opaque whiteness 

 changes to a translucent pale amber colour. Methods, therefore, 

 of rapidly drying the wet rubber have been introduced. The 

 quickest way is by means of the vacuum dryer. The removal 

 of moisture by this apparatus entails a fairly high temperature, 

 which appears to have a somewhat detrimental effect on the 

 quality of the rubber. The best means of drying the newly 

 formed rubber is still undecided, and the problem is to some 

 extent bound up with that of curing. 



One estate is turning out a variety of rubber known as 

 " block," which is much appreciated. It is made by compressing 

 in a special manner dry sheets or other thin forms. There are 

 distinct points in favour of marketing plantation rubber in this 

 shape. It is convenient to handle, and less surface is exposed 

 to oxidising influences. If the blocks be made not more than 

 an inch in thickness, their homogeneity can easily be verified. 



If blocks be made direct from the clots, then the difficulty 

 is to dry them in short enough time to prevent moulding and 

 putrification. Here is shown the value of a preservative. 

 Willis and Bamber l a few years ago turned their attention to 



1 Willis and Bamber, Circ. and Agric. Journ., R.B.G. Ceylon, 1907, 4. 

 No. 1. 



