RUBBER 



411 



The above table shows the tremendous strides in production of plan- 

 tation rubber, the almost stationary production of wild rubber from 

 Brazil and the falling off in the product from all other sources, such as 

 Central America, Mexico, Africa, the Guianas, etc. 



METHODS OF MANUFACTURE i 



Wild rubber contains many impurities such as dirt, stones, bark, 

 leaves, chips, etc., as it comes to this country in its crude state in the form 

 of biscuits or balls. The first process, therefore, in the manufacture of 

 the various finished forms of rubber is thoroughly to cleanse it of all 

 foreign matter. Wild rubber, which is generally called Para rubber from 

 Brazil, contains a great many more impurities than the plantation rubber. 



1900 1902 1904 1906 1908 1910 1912 1914 1916 1918 



Years 



Fig. III. — Curve representing the world's production of India rubber from 1900 to 1918, 



inclusive. 



The latter comes to this country in sheets or packages and is much more, 

 free from impurities on account of the greatly improved methods of col- 

 lecting and coagulating the latex. 



The process of cleansing consists of washing the crude rubber in hot 

 water for a period of about twenty-four hours. It is then passed through 

 corrugated rollers in the presence of large quantities of water. This 

 process removes the impurities and gives the rubber a more homo- 

 geneous structure. It is then placed in the drying rooms 'a sheets and 

 after a thorough drying it is stored until desired for further use. 



' The methods of rubber manufacture is a large and involved subject and can be cov- 

 ered only in a most brief and suggestive fashion in this work. For further reading on the 

 manufacture and the chemistry of rubber it is suggested that several references in the bibliog- 

 raphy at the close of this chapter be consulted. 



