Gums, Resins, 



20 



of the rubber globules. When the latex comes from the tree the rubber globules are 

 in masses. These masses get broken up by the straining, and still further broken up 

 by the washing until by the third washing nearly all the globules are separated. 

 These single globides become water-soaked and get heavier. Each washing settles 

 more slowly. The single globule, being microscopic, cannot be seen, and is lost if 

 widely separated. Sometimes the third washing refuses to settle at all. Besides all 

 these, there is a danger of coagulation if latex is washed too much. The latex 

 behaves very irregularly in this respect. Apparently the temperature affects it as 

 much as anything else. On a warm day it sometimes coagulates at the first washing. 

 The rubber coagulated in this manner forms in a large cake at the top of the wash- 

 ing can, and must be cut up and the water squeezed out by a clothes wringer or 

 rolling pin. This rubber is strong, clean and fairly dry, but is not uniform, and 

 never can be as dry as thinner strips coagulated regularly by the blotter method. 



Coagulation can be avoided by washing the latex carefully stirring it pretty 

 often, and not letting it stand long after it has settled. It also might be prevented 

 by the addition of some chemical, such as formaldehyde or ammonia. Formaldehyde 

 is placed in the latex in the field to keep it from coagulating. I have never observed 

 anything which proved that it did this, and I have sometimes seen latex brought in 

 with small pieces of rubber floating in it. All these things go to show that too much 

 washing is bad. Whether the black water is harmful to rubber or not, I cannot 

 determine. Pieces of rubber washed once, twice, and three times all have the same 

 strength, elasticity, and cleanliness from bark. There is a difference in the colour ; 

 that washed most being lightest, the unwashed rubber being almost black. There is 

 also a difference in stickiness. Unwashed rubber loses its stickiness it dried long 

 enough. Rubber which is unwashed or washed very slightly resembles most nearly 

 in colour a piece of Ceylon Para. 



As stated before, the fine bark can nearly all be got rid of by washing. This 

 is due to the fact that the bark is heavy, and settles in the bottom of the washing 

 can and runs out with the first rush of black water. The latex may be stirred and 

 allowed to settle for a few minutes, and then the first black water be run off, carry- 

 ing the bark that has settled with it. It is then stirred again, etc., each stirring 

 loosening more bark from the latex and allowing it to settle, until practically all 

 is gone. 



COAGULATION— WET AND DRY METHODS- 



There appear to me to be two general classes of coagulation, which I call wet 

 coagulation and dry coagulation. Dry coagulation is the taking away of water 

 in some manner, leaving the solid parts of the latex globules, which are nothing 

 more or less than rubber. Wet coagulation is the process of addition of some 

 chemical, or of boiling or some similar method which causes the albumin to coagu- 

 late, drawing the latex globules together while still wet. The rubber formed by dry 

 coagulation should be free from moisture, and generally is so, because the rubber is 

 formed when still wet. Unless it is in a thin sheet, however, moisture is shut 

 inside of it where it cannot be easily got out. Wet coagulation has not always this 

 objection, for the methods used in Ceylon would be classed as wet coagulation, and 

 yet they make very good dry rubber. 



Of dry coagulation the simplest method is to allow the latex to remain 

 on the tree until coagulated. This makes good rubber, which is pretty clean 

 unless trees have made moss on them. This rubber is not always dry if it rains 

 between the time of coagulation and time of gathering. If allowed to stay on 

 the tree very long it becomes very sticky, which I believe is due to getting 

 wet and drying out as?ain many times. I think this is the reason why people 

 state that sun-dried rubber is sticky. It has been my experience that rubber 

 dried in the sun is not stickier than other rubber if it is not in the sun too 



