188 



THE INDIA RUBBER WORLD 



[March i, 1904. 



able. But such information, without the ability to apply it, 

 which can only be acquired through long experience, can be of 

 little or no value to its possessor. 



It is evident therefore that opinions concerning the process 

 as to how it is or should be conducted are absolutely of no value 

 unless they are expressed by persons having perfect familiarity 

 with every part of the art. Because one manufacturer conducts 

 his operations in a certain manner, it cannot be said that 

 another manufacturer who proceeds differently does not under- 

 stand the art as well as the other. 



When vulcanization was first discovered only Paia rubber 

 was known, and vulcanized rubber had a very limited applica- 

 tion, being largely confined to articles for personal use. Since 

 that time a large number of varieties of rubber have been dis- 

 covered, none of which however are equal in value to Para rub- 

 ber, and all of which must be treated differently. If the manu- 

 facturers of today had only Para rubber to deal with, and if 

 the public were willing to pay a fair price for goods of a high 

 quality made from it, the art would be comparatively easy to 

 practice. But the ever increasing demand of the public for 

 cheaper goods, having, however, the same appearance as those 

 of a high grade, compels the manufacturer to be continually 

 devising expedients to meet it. The most natural course to 

 meet this demand is to employ cheaper rubbers, and to adulter- 

 ate the compounds with substitutes and the various filling in- 

 gredients. To make such changes is generally difficult for the 

 manufacturer. 



To the ordinary observer it would seem perfectly simple to 

 employ cheaper grades in place of the high grades. He can see 

 no more difficulty in doing this than there would be in substi 

 tuting in a leather shoe a cheaper grade of leather in place of a 

 high grade — a substitution which is very simple and which only 

 results in another grade of goods. 



It must be considered, however, that the cheaper grades 

 which constitute about half of the world's production of rubber 

 cannot be worked, compounded, or cured in the same manner 

 as when Para rubber is used. For instance — if a compound 

 consisting of 12 pounds dry fine Pata rubber, 6 pounds litharge, 

 6 pounds whiting, and 6 ounces of sulphur, a very common 

 compound, be submitted to the ordinary dry heat temperature, 

 it vulcanizes readily in 32 minutes, or in 12 minutes if the vul- 

 canizing atmosphere be impregnated with sulphur, the tempera- 

 ture being the actual temperature of the rubber itself. If, how- 

 ever, upper Congo red balls, one of the best grades of African 

 rubber.be substituted for the Para in this compound, there is 

 not the slightest trace of vulcanization in 32 minutes if heated 

 in air — nor in 12 minutes if the atmosphere be impregnated with 

 sulphur. Neither is there any trace of vulcanization after an 

 exposure of an hour or even two hours, though the percentage 

 of sulphur be increased to 5 percent. When the vulcanization 

 does take place after a longer exposure the result is unsatisfac- 

 tory. If the vulcanizing medium be metallic without pressure, 

 which will effectually exclude the air during the submission of 

 the compound to heat, the same compound requires an hour 

 for vulcanization instead of the 32 minutes, thus showing that 

 the difficulty is inherent in the rubber itself and not the result of 

 any injurious action of the air. But this process cannot be sub- 

 stituted for the usual dry heat process. To successfully employ 

 one of the cheaper grades of rubber in the dry heat process in 

 place of Para or to employ one of the numerons substitutes that 

 are on the market, or to use a much larger quantity of whiting 

 or other adulterant, requires a whole series of experiments on 

 the part of the manufacturer before he can learn how to make 

 the necessary changes in his process, and after that, many 

 more of less unsuccessful trials on the part of the workmen. 



It does not follow at all that because certain of the cheaper 

 grades of rubber can be successfully vulcanized by one process 

 that they can be successfully vulcanized by another process. 

 Certain grades of rubber that are vulcanized by the steam pro- 

 cess have hitherto resisted all attempts to vulcanize them by 

 the regular dry heat process. Neither does it follow that if the 

 manufacturer is successful in thus cheapening his compound 

 that the goods made from it will prove durable. It is therefore 

 necessary before putting them on the market to lay samples 

 aside for many months in order to ascertain whether the com- 

 pounds are durable or not. If they stand this test the manu- 

 facturer should even then lay aside further samples of the 

 goods to guard against possible elements of decay which often 

 do not show themselves until after a year or two. 



A well known illustration of the necessity of following this 

 practice has been seen in the experience of one of the largest, 

 best equipped, and best managed factories in the United States, 

 and one that has at its head the best expert talent that can be 

 found in the world. Some time since, not more than two or 

 three years or so, it was found that the goods of this company 

 which had been distributed among the trade were proving de- 

 fective after being used. As time passed, more and more re- 

 ports of defective goods were received. These increased to 

 such an extent that a thorough investigation was made, when 

 it was found that quite a portion of the goods made in this fac- 

 tory during several months were proving to be defective. But 

 this was not the end of the trouble. The defective goods had 

 become so mingled with sound goods that it was found practi- 

 cally impossible to separate the sound from the unsound. It 

 was therefore necessary to recall a very large amount of goods 

 that were in the dealers' hands, and to sell these with all 

 others on which any suspicion could be cast, for what they 

 would bring as uncound goods. 



And yet these goods had been daily examined thoroughly by 

 the best expert talent to be found and passed as sound goods. 

 As none of the defects developed for several months, and as a 

 year or more elapsed before the extent of the damage was as- 

 certained, it can be readily seen that the loss on these goods 

 must have been very heavy, whereas if the defects could have 

 been discovered at the time the goods were made or within a 

 short time afterwards, the defects coulo have been remedied, 

 and the loss thus reduced to a moderate amount. 



It is thus seen that the art of vulcanization is by no means a 

 simple one ; that it cannot be learned from books or formulas 

 and that long experience is necessary for its successful prac- 

 tice ; that it is applied only to rubber which has been properly 

 compounded and worked, and that the result of applying the 

 usual formulas in the final vulcanizing process depends entirely 

 on the manner in which such compounding and working has 

 been performed ; that it is difficult for the manufacturer to use 

 cheap grades of rubber or substitutes in place of Pari rubber, 

 and, that when such substitution has been apparently success- 

 ful, the greatest care must be taken to prove the durability of 

 the goods made from the changed compounds. 



One of the greatest fields in the art for investigation at the 

 present, if not the greatest, is to discover means whereby the 

 cheaper grades, which have the same chemical composition as 

 the Para rubbers, may be vulcanized by the dry heat process 

 so as to equal the latter in strength and durability. 



A Tariff Decision.— An importer of rubber recoil pads at 

 Portland, Oregon, claimed them to be dutiable as manufactures 

 of India-rubber, but the collector imposed the rate of duty on 

 " parts of guns," which was confirmed by the general appraisers 

 when an appeal was made. 



