(}ums, Resins, 



10 



[July, 1908. 



cording to this new method, claimed 

 that it was Para rubber, and another 

 manufacturer was highly interested 

 thinking that the sample was some new 

 rubber of some unknown plant. 



Another point in connection with this 

 method of preparing rubber I shall now 

 refer to. As you know, the Brazillian 

 rubber collector prepares the crude pro- 

 duct by dipping a spade-like piece of 

 wood into the latex and then drying 

 the thin film of latex over the smoke 

 from burning palm nuts- When the 

 film is solid, another one is added, and 

 thus the work goes on, until a large ball 

 of rubber has been formed. Each of the 

 succeeding films exerts a certain pressure 

 on the inner parts, and in this fact we 

 have to look for one of the main rea- 

 sons why so-called hard cure Para 

 retains its strength so well. Another 

 observation is that, if a piece of crude 

 rubber is surrounded by twine as in a 

 cricket ball, the rubber remains perfectly 

 sound for years, while if a piece is ex- 

 posed to the atmosphere and is not 

 subjected to pressure it will in the same 

 period of time lose many of its physical 

 qualities. I attribute the keeping quali- 

 ties of Para balls and of the rubber in a 

 cricket ball to the pressure to which 

 it is exposed in either case. Experiments 

 have shown that pieces of freshly coagu- 

 lated rubber which have been subjected 

 to very high pressure retain all the 

 characteristics of good rubber much 

 longer than pieces not pressed. 



It is further important to notice that 

 hard cure Para rubber is not perfectly 

 dry. Experiments have shown that 

 rubber containing a slight amount of 

 moisture is more " elastic," has a high 

 resiliency than rubber not containing 

 any moisture. Other experiments have 

 shown that perfectly dry rubber does 

 not keep as long as a rubber containing a 

 certain amount of moisture. 



On the other hand, if the amount of 

 moisture is too large the rubber is liable 

 to deteriorate, as the moisture assists 

 bacterial organisms in their destructive 

 processes. With these points in view 

 the method of drying and pressing rub- 

 ber employed in the just described 

 system of preparation was developed. 

 In drying the strips of crepe rubber 

 until they contain about 6 or 7 % of mois- 

 ture the excess water is extracted and 

 the rubber is left with a suitable amount 

 of moisture to retain all its physical 

 qualities. As I mentioned, the rubber 

 is blocked in this condition. The so- 

 called "fixing" of the block, or its 

 rapid drying until the outer part to a 

 depth of about 5 mm. is perfectly dry, 

 results in this outer layer contracting 



and exerting a pressure on the inner part. 

 When such a block of rubber is cut open, 

 it will be noticed that there is a slight 

 difference between the outer layer and 

 the inner part of the block, the latter 

 being superior in quality. 



In regard to Castilloa rubber, it is 

 important that as small a surface as 

 possible is exposed to the atmosphere, 

 as it is very liable to oxidize. From this 

 point of view it is evident that the block 

 form is th9 most suitable. For shipping 

 purposes the block is also the most handy 

 form. 



Tackiness of Rubber.— The develop- 

 ment of tackiness in Castilloa rubber has 

 been studied to some extent at La Zacu- 

 alpa Laboratory. Many experiments with 

 inoculation of bacteria, which cause 

 tackiness, have been made, and it has 

 been proved that tackiness can be pre- 

 vented by the use of one or another dis- 

 infectant in the preparation of the crude 

 rubber. Following up the cue given 

 by the method of coagulation employed 

 in the Amazon district, most experi- 

 menters first used creosote as antispetic 

 in preparing rubber. It had been found 

 that the smoke of the urucuri nuts con- 

 taired among other substances, small 

 amounts of creosote, acetic acid and 

 acetone. My experiments have shown 

 that a great number of diffeient chemi- 

 cals can be used in asseptizing the latex, 

 but an alcoholic solution of creosote 

 in small quantites is probably one of 

 the best. 



Packing.— It is of importance that in 

 packing rubber blocks for shipping per- 

 fectly clean cases be employed, and no 

 paper or other substances should be 

 placed with the rubber in the cases. It 

 is not advisable to make the blocks 

 heavier than about 25 lbs. Four of these 

 blocks can then conveniently be packed 

 in one case, which thus contains from 

 100 lbs. to 1 cwt. 



Cleanliness.— I may add that in all 

 the processes of rubber preparation the 

 strictest cleanliness should be observed. 

 The latex factory should be as scrupu- 

 lously clean as a dairy. How different is 

 not this idea from the general method 

 of rubber making employed at present 

 in Mexico. 



Storing Rubber.— Rubber prepared 

 i n a proper manner can be stored on 

 the plantation for a long time. Experi- 

 ments have shown that one year of 

 storage in a tropical climate does not 

 perceptibly affect the rubber which has 

 been prepared well. In passing, I 

 may here mention that it is advisable 

 to have a store room supplied with 

 orange or ruby coloured windows in 



