September i, 1908.] 



THE INDIA RUBBER WORLD 



401 



Alum for Coagulating "Castilloa" Latex. 



To THE Editor of the India Rubber World: At the July 

 meeting of the Camara Agricola de Palenque, nine of the 

 fifteen rubber plantations of this district were represented. 

 Following a general discussion on rubber culture, mode of 

 tapping, coagulation, etc., it was suggested and requested that 

 the president of the Camara answer through the columns of The 

 India Rubber World an article on "The Coagulation and Curing 

 of Rubber" that appeared in the July number of said journal 

 [page 326], giving the process in use by some of the companies 

 represented in this Camara. 



Mr. Elmer A. Schmidt, manager of the Rio Michol Rubber 

 Plantation, the pioneer of this mode of coagulation here, has 

 kindly furnished a description of his process, which I enclose. 



H. H. MARKLEY, 

 President Camara Agricola de Palenque. 

 Luinija, Estado Chiapas, Mexico, August 4, 1908. 



Mr. II. II. Marklev, President of the Camara Agricola de Palenque, 



Finca Lumija: 



Dear Sir : I am pleased to 

 conform with your request to 

 give a description of the meth- 

 ods by which we obtained the 

 rubber shown you and th>- 

 members of our association at 

 our last meeting. As we have 

 used the process for nearly a 

 year on latex of wild and also 

 planted trees, we had oppor- 

 tunity for the time test also, 

 and find the product stood it 



• welt. 



As it may be interesting to 

 know what other methods we 

 had used, before we came to 

 use this one, now exclusively, 

 I will describe them in short. 

 On this plantation, which has 

 a big amount of wild rubber, 

 besides the planted trees, we 

 have been tapping continually 

 during many years, coagulat- 

 ing the latex by the process 

 known to the Indians of this district, namely the juice of a vine 

 called "bejuco" and also "nata," and common soap or the lye 

 of wood ashes, boiled in water. The product was not bad, but 

 it would give out a nauseating odor when exposed to the sun. 

 and after keeping some time would become tacky. Another 

 inconvenience was that with the increasing need of the "nata" 

 vine when our young rubber would come into bearing, we 

 would have to cultivate the vine or else look for another way 

 of coagulation. Then we tried common water, but to. get re- 

 sults still had to use "nata" and soap. The rubber came oul. 

 very clean, but the process was slow, and it would get tacky ac 

 times; perhaps, however, this was due to the varying quality of 

 the soap obtainable here. 



Eventually we got acquainted with the process used in Cey- 

 lon and tried it here, but neither the acetic acid, the formaline, 

 nor the other chemicals used with the Hevea rubber gave the 

 good results expected from them, until, by looking up the 

 chemical properties of rubber in the good old book called "United 

 States Dispensatory," we found alum mentioned as a coagulating 

 agent for rubber, which we tried with the e.xcellent result you 

 know. The very simplicity of the process, which needs no ma- 



Seven-Yeak-Old "Ca^tilloa" Kuiirer. 



[On plantation "Iowa," near Salto de Agua, Estado Chiapas, Mexico, 

 owned by the German-.American Coffee Co., of New York. Planted iz x 12 

 feet: some are 28 to 30 inches in girth, and 40 to 50 feet high.] 



chinery, recommends it where skilled labor cannot be obtained 

 without high pay and difficulty. At the same time the rapidity 

 with which the rubber is obtained is of great importance. 



We use here cylindrical tanks made of corrugated sheet iron 

 one meter [=39.37 inches] high by ]/> meter wide, with a 

 faucet attached to the side, level with the bottom. Into this tank, 

 the latex, not exceeding 10 -kilos [^22 pounds] per tank, is 

 poured through a strainer made of mosquito screening, which 

 retains pieces of bark and other impurities. After rinsing the 

 strainer we fill the tank nearly to the top with water, leaving it to 

 rest over night, and next morning the rubber will have separated 

 sufficiently from the water, which has obtained a black-greenish 

 tinge, and can be drawn off through the faucet, taking care that 

 when it changes into milkish yellow, the drawing off operation 

 to be suspended. The latex, thus cleaned from all its soluable 

 impurities, is now poured into a vessel in which about a table- 

 spoonful of powdered alum had been dissolved previously in 

 about 2 liters [^2.11 quarts] of water, the tank being cleansed 

 with little quantities of water which are all poured in. The 



coagulation will then be per- 

 fect and can be seen by taking 

 a sample out w-ith a glass 

 when can be seen cream-like 

 corpuscles of rubber floating 

 towards the top. 



Meanwhile, you will have 

 -pread some moist, light cot- 

 ton cloth over wooden frames, 

 fastened with spikes and pour 

 the rubber on it, first in small 

 quantities, gradually increas- 

 ing the amount and then let 

 it drain off. In about two 

 hours most of the water con- 

 taining the alum in solution 

 will have run off. leaving the 

 rubber in a soft creamy condi- 

 tion. This can be easily 

 scraped off and worked with 

 the hands into cakes in very 

 short time. These cakes are 

 cut into bands which are hung 

 to dry, two days being suffi- 

 cient imder ordinary conditions. These strings of rubber rolled 

 up into oblong balls of from 10 to 25 kilos are then ready for 

 shipment. 



With reference to our tapping, I must say that the machete 

 has been discarded long ago and of several instruments and 

 tools tried, including those of the Malay States and Ceylon, we 

 have finally adopted one which gives good result in tapping the 

 wild as well as the planted trees. It consists of a rather wide 

 "U" shaped steel band of the width of a handsaw, which is 

 fastened to a wood handle. This handle has a long set screw 

 passing through it. regulating a steel band by forcing it away 

 from the handle to which it is attached through screws, there- 

 by controlling the depth of the cut and serving at the same 

 time as a protector to the knuckles of the tapper. 



We take care to set the tool shallow enough not to injure 

 the cambium, but after the cut, whioh removes the bark, has 

 been made, w-e have the operator run a sharp knife the length 

 of the cut. This sets the latex flowing more freely and as it 

 closes right away does not injure the tree by letting in air to 

 woody portions. We have been tapping trees from 18 inches cir- 

 cumference to up to the biggest wild trees, with satisfactory 



