June 1, 1913.] 



THE INDIA RUBBER WORLD 



463 



The Washing of Crude Rubber. 



CRUDE RUBBER as it comes to the market appears in a 

 great variety of forms — hams or pellcs, balls, strips, saus- 

 ages, lumps, flakes and all conditions of scrap. In all of these 

 forms there is more or less foreign matter — matter that must 

 be removed before the rubber can be used in manufactured 

 goods. Tlu- fiiroian sulistMnces ;irc bits of bark, leaves, splinters 



Knife for Cl'ttixg Rubber Biscuits. 



■of wood, sand, fibre, earthy matters, etc., etc. The only ex- 

 ceptions to this very general rule are dercsinatcd and plantation 

 rubbers. Many manufacturers find it worth their while to wash 

 even these sorts, as the process seems to result in a better and 

 tougher product. The primary process, whatever the Hne of 

 rubber manufacture, therefore, is that of washing. 



The gum is usually put into a pickling tank containing warm 

 water, where it is allowed to soak. This removes foreign matter 

 on the surface, softens the rubber and makes it more easily 

 worked. This tank is usually sunk to the level of the floor near 

 the washers to facilitate the handling of the rubber. For some 

 grades, such as pelles of fine Para, a power-driven circular knife 

 is used for cutting the rubber into smaller pieces, that they may 

 he more easily sheeted. The rubber thus prepared is fed into 

 tlie first washing machine or cracker. The action of this ma- 

 chine is to tear or mangle the rubber, releasing the dirt and 

 bark, which are washed away during the operation by a stream 

 of cold water, which plays upon the mass. The cracker is a 

 heavy, powerful, two or three-roll type of machine, the size and 

 number of rolls depending on the qua.itity of material to be 

 handled. 



After a thorough washing in the cracker the partially cleaned 

 rubber passes to the two-roll washer. The province of this ma- 

 chine is to complete the washing process and to sheet the torn 

 rubber. Warm water is used on the tough mass to produce a 

 degree of stickiness, that the action of the rolls may form it 

 into sheets. Cold water is then turned on and the sheets 

 passed through the rolls repeatedly until completely cleansed by 

 the kneading action of the rolls and the running water. 



There is a great variety of washers in use in the world's rub- 

 ber mills, but a majority of them are of practically the same 



design; ihat is, lliey arc usuall> lun-roU machines, the rolls 

 geared in different speeds and running toward each other. In 

 rubber plantations practically the same type of a machine is 

 used, run either by hand or by power, and in some of the larger 

 plantations batteries of machines are employed. As plantation 

 rubber is washed very soon after coagulation, the machine may 

 be quite light and does not take nearly the amount of power 

 to run that the same types in rubber factories call for. When 

 it is remembered that crude rubber shrinks anywhere from 12 

 to 50 per cent., that while a considerable percentage of the shrink- 

 age is due to the water extracted from the rubber, a great deal 

 is foreign matter, more or less injurious to the gum, it will be 

 wondered at that manufacturers have not insisted upon rubber 

 being washed at the source of supply and delivered clean and 

 dry, thus saving much in the way of freights. The explanation 

 is that as soon as rubber is massed and its physical aspect 

 changed, it is so easy to amalgamate the inferior and superior 

 qualities that manufacturers decline to take the risk of being 

 cheated, and have consistently frowned upon all such sugges- 

 tions. There have been, however, and still are, crude rubber 

 washing companies in various parts of the world that have 

 done a fair business, but none of them have been conspicuously 

 successful as yet. 



There are some forty companies in the world making roll 

 washers, and their patterns are more or less similar. It will, 

 therefore, be sufficient, in describing these machines, to take ex- 

 amples from the output of any of the higher class of machine 

 manufacturers and describe them as practically typical of the whole. 



Roll washers consist of heavy iron rolls running toward one 

 another, set in substantial iron frames, fitted with piping so that 

 hot or cold water may be sprayed over the rubber as it passes 

 between the moving rolls. These rolls, be it remarked, are 



Pl.vntation H.vnd \\ asher. 



fluted or corrugated so as to bite the often intractable and 

 slippery gum. 



Regarding the kind of roll — corrugation, many experiments 

 have been made to determine the best possible form. There 

 is for example the saw-tooth corrugation, in some cases both 



