July, 1908. 



Saps and Exudations. 



One of the first methods of mechani- 

 cally preparing rubber was by means of 

 centrifugal force. A separator, built on 

 somewhat similar lines to those of an 

 ordinary cream separator, was used with 

 success. 



The latest method of preparing rubber 

 on a commercial scale is one which I 

 developed after numerous experiments 

 at La Zacualpa Botanical Station and 

 Rubber Laboratory. I shall here briefly 

 describe this system, which has recently 

 been patented. (Diagram of a rubber 

 factory was shown.) 



I shall here show a diagram of a plant- 

 ation rubber washing, drying and press- 

 ing plant according to the system re- 

 ferred to. The latex, when brought in 

 from the field, is weighed on the scales 

 P. placed on an elevated platform. It is 

 then poured into A, the latex receiving 

 tank, where it remains until the coagul- 

 ating process remains. If it is necessary 

 to keep the latex from coagulating for 

 some time, a small amouut of formalde- 

 hyde is mixed with the latex. 



From the receiving or storage tank A. 

 the latex passes into B., a centrifugal 

 strainer, in which all mechanical im- 

 purities are separated. The latex now 

 runs into C, a special coagulating con- 

 veyor. This coagulatoris provided with 

 a steam heated jacket, so that the tem- 



?erature of its contents can be raised, 

 'he latex is mixed with an equal quan- 

 tity of water, and an alcoholic solution 

 of creosote is added in order to thorough- 

 ly disinfect the resulting rubber. The 

 temperature is raised to about 50° C, 

 and the latex is slightly stirred by the 

 movement of the conveyor. When the 

 rubber commences to coagulate, which 

 process begins in about 20 minutes, it is 

 forced by the conveyor into the cream- 

 ing vats D, and D,, where it is allowed 

 to stand for a short while. The latex 

 is further diluted with water entering 

 underside of these vats. Upon being 

 allowed to rest a creaming begins, and 

 when separation has taken place some 

 of the serum is drawn off from the 

 lower part of the vat, and new clean 

 water added from below. This washing 

 of the cream is repeated several times 

 in order to separate as much as 

 possible of the resins contained in 

 the latex, which have been kept in 

 a fluid state by the warm water. 

 Finally, the cream is allowed to rise, 

 and the surface is raised by the in- 

 jection of water allowing the cream or 

 partly coagulated rubber to run over an 

 overflow lip on to tables fixed beneath 

 the lips of these vats. The rubber is 

 partly worked by hand with small 

 wooden spades, and passed to the wash- 

 ing machines F. In these the rubber is 



pressed between heavy steel rollers, and 

 at the same time it is further washed 

 with water. The rubber is put through 

 these machines several times until it 

 appears in the form of fresh crepe rubber. 



All serum or washing water drawn off 

 is passed through a separator E. in which 

 all the rubber contained in the water is 

 extracted. 



The strips of crepe referred to are 

 placed in the vacuum dryer J. until 

 only 6 or 7 % of moisture remains. The 

 strips of dry rubber are then folded and 

 placed in the box of the press G, in which a 

 sufficient pressure is applied. In this 

 manner a block of rubber is obtained, 

 which contains the maximum amount 

 within a minimum of space. In order to 

 keep the presses continuously going inter- 

 changeable boxes are introduced, and 

 by a duplicate bridle arrangement fitted 

 with four strong screws the inverted 

 name plate for branding the rubber, 

 is held down by these screws and easily 

 relieved from the foot on the press. The 

 press ram screw is then raised, a new 

 name inserted, and another box placed 

 in position. After pressing, the boxes 

 with the rubber still under pressure are 

 taken to another stove for "fixing," and 

 then by simply unlocking the hinged base 

 the branded and finished block is thrust 

 through the bottom. These rubber 

 blocks are made of a standard size, and 

 packed in suitable standard packing 

 cases, well planed on the inside, and 

 they are then ready for shipping. 



The complete plant for preparing 

 crude rubber, as here described, is made 

 by Messrs. David Bridge & Co., of 

 Castleton, Manchester, England, and 

 costs, complete with boiler, engine, 

 shafting, circular saw, planer and ma- 

 chinery referred to, about $13,000 Mex. 

 Such a plant has a capacity of 300 lbs. 

 dry rubber per day. 



Quality of Rubber.— The rubber pre- 

 pared by this method has been pro- 

 nounced fully equal to best hard cure 

 Para, which, as is well-known, is the 

 best rubber on the market. The prices 

 offered for this new Uastilloa rubber are 

 higher than current prices for ordinary 

 Para. 



A general fault previously found with 

 Castilloa rubber is the large amount of 

 resin which it contains. The percent- 

 age of resin in Castilloa rubber has 

 varied from 8 to 41 %. By this new 

 method of preparation the amount of 

 resin can be lowered to less than 3 %. 

 This new rubber therefore fills the re- 

 quirements placed upon rubber articles 

 by the British Admiralty. It is curious, 

 but a well-known rubber buyer, to 

 whom I showed a sample, made ac- 



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