RUBBER AND RUBBER MANUFACTURE 5097 RUBBER AND RUBBER MANUFACTURE 



THE STORY OF RUBBER 



UBBER AND RUBBER MANUFAC- 

 TURE. Where does rubber come from? Do 

 we dig it out of the ground? Does it grow 

 on trees, or is it made by combining a number 

 of different substances? Probably many boys 

 and girls have asked themselves these ques- 

 tions without finding a satisfactory answer. 

 Rubber does not grow on trees, but it is ob- 

 tained from a number of trees, shrubs and vines 

 that grow in hot countries. 



How Rubber is Obtained. We are all familiar 

 with the milkweed (which see), and know that 

 it is so named because of its milky juice. Ex- 

 periments lead us to believe that there is a lit- 

 tle rubber in this juice, but the quantity is so 

 small that it would take cartloads of milkweed 

 to give us enough rubber to make a small rub- 

 ber ball. There are, however, in the valley of 

 the Amazon, in the central part of Africa, in 

 the East Indies and in some parts of Mexico 

 and the southwestern part of the United States 

 a number of plants from which rubber is ob- 

 tained in paying quantities. The most impor- 

 tant of these plants is the hevea, or rubber tree, 

 as it is commonly called, and it is from the 

 milklike juice of this tree that most of the rub- 

 ber is obtained. 



i an incision is made through the bark, 

 the juice flows out slowly. The trees are 

 "tapped" by cutting slanting grooves in them. 

 A small cup is fastened to the tree at the lower 

 end of the groove to collect the juice, which 

 is gathered every evening. A pail of this juice 

 looks somewhat like a pail of milk, and if it is 

 allowed to stand for several hours, the rubber 

 will rise to the surface like cream. The gath- 

 erer makes a smoldering tm of leaves and a 

 kind of nut that grows in the forest, then takes 

 a wooden paddle, dips it into the juice and 

 holds r fire until tl,. ,.s been 



evaporated, leaving a thin coat of rubber on 

 it <lips the paddle again 

 and holds it on th,- lire, and con- 

 tinues to repeat the process until his paddle is 

 covered with a thick coat of rubber. He then 

 cuts this open on one side, takes it from the 



paddle and rolls it into a ball, like those shown 

 in the picture. These balls are collected and 

 shipped to market. 



The average tree yields about two ounces of 

 juice a day. One-third of this weight is rub- 

 ber, and about ten pounds of rubber are ob- 

 tained from a tree in a year. The rubber 

 obtained from the hevea tree by this process 

 is of the highest quality and is known as Para 

 rubber, because it is shipped in greatest quan- 

 tities from the city of Para, in Brazil. 



While the greatest part of the rubber of 

 commerce is obtained from the juice of certain 

 trees and vines, no inconsiderable quantity is 

 obtained from shrubs, vines and trees in which 

 it occurs in solid form in stems and roots. The 

 Congo region in Africa abounds in plants of 

 this sort. The guayule, a shrub growing from 

 three to five feet high, is becoming an impor- 

 tant source of rubber. This plant is of special 

 interest because it is found in Northern Mexico 

 and in the southwestern part of Texas, and 

 because it can be cultivated in these regions 

 and in Arizona, where large plantations are in 

 successful operation. 



Uses of Rubber. Rubber is used for so many 

 purposes that were the supply cut off a number 

 of important industries would be destroyed. 

 We should have no rubber boots or shoes; we 

 should have to find some other waterproof 

 material for our raincoats; pneumatic tires, in 

 universal use for bicycles and automobiles, 

 would have to be replaced with those of a less 

 desirable material and we should be obliged 

 to do without telephones until some other ma- 

 terial as comt m< nt and not a conductor of 

 electricity could be found to take its place. 

 Besides these greater uses for which rubber is 

 employed it enters into the manufacture of 

 many small articles which have become indis- 

 pensable in the homo and the office, such as 

 combs, buttons, rubber bands, erasers and foun- 

 t.un pens. 



The importance of rubber in modern war- 

 fare may be realised in a measure from the 

 following incidents: 



