December 1, 1S13.] 



THE INDIA RUBBER WORLD 



119 



shall we be surprised to find that the physical and mechanical 

 conditions of the coagulation, and the drying, also, all play a 

 most important part. 



Numerous explanations have been attempted with a view to 

 making this superiority of the Amazon product comprehensible. 

 One of the latest is that of Dr. W. Esch, who claims that the 

 rubber manufactured in Brazil contains a smaller quantity of the 

 salts pre-cxistent in the latc.\ than the coagulum obtained in a 

 mass hf the addition of a coagulating solution — acetic acid for 

 instance. This supposes that in the bassia (a sort of large 

 metallic bowl into which is poured the latex that is to serve for 

 coating the ball in the course of manufacture) there has been a 

 beginning of the "creaming" so that the upper layers are richer 

 in globules and the lower strata contain more of water and of 

 salts. Dr. J. Huher indicates that he has never observed anything 

 like this. I may state that this separation seems very improbable 

 to me. The ciiya, or cup, which the seriitgtteiro uses to take 

 from the bassia the latex for pouring over the ball, is plunged 

 every minute into the mass of latex and insures a sort of con- 

 tinuous mixing. 



We know, moreover, that if there are applied to the latex some 

 of the effects produced by smoking, w'C obtain as a result inferior 

 qualities — for instance, with acetic acid, with hot air or steam 

 under pressure (Cross experiments), or by simple evaporation 

 (old experiments by Wickham). 



We see, therefore, that all the methods hitherto devised only 

 slightly resemble smoking. Some are but remotely similar, such 

 as the acetic acid process, in which only one of the chemical ef- 

 fects possible is realized, which can only play a certain part in 

 the coagulation but not in the preservation, for here we operate 

 cold, pressing the coagulum on the machine relatively quickly, 

 and in the form of sheets, biscuits and blocks. 



It seems to me that of the smoking machines thus far brought 

 out the greater part are far enough from realizing the Ama- 

 zonian process. According to the brief descriptions which I have 

 seen, the Wickham apparatus is possibly- that which most closely 

 approaches it. The author believes that materials found in the 

 East could play the same part as the fuel used in Brazil. I will 

 not contradict this, inasmuch as I have stated that the fumes 

 are sometimes produced by the burning of green wood of no 

 special variety. 



Nevertheless, will it be possible to replace, by a machine, the 

 work of the seriugueiro? I do not wish to maintain that smok- 

 ing is a work of art ; but it is, nevertheless, a trick, a knack to 

 be acquired, an intelligent performance of the operator, who does 

 not always work in precisely the same manner. 



To obtain a well-coagulated ball, we require a determined 

 fluidity of the latex. Too watery a latex cannot yield a good 

 result. Fumes of a certain quality are also required (which the 

 workman recognizes by their pale color), issuing in a jet of the 

 desired strength. If these characteristics disappear he stops the 

 operation and refills the stove with this or that fuel. The ad- 

 mission of air to the bolhao is regulated so as to promote or re- 

 duce the draught. 



The seriugueiro decides for each layer how long a time should 

 elapse before he withdraws the ball from the effect of the smoke 

 and dips it into fresh latex. This period is not always the same. 

 I have noted variations from the normal period to three times 

 as long for a small plancha. Only an experienced workman can 

 appreciate at sight the requisite time. It is necessary, in fact, to 

 cease smoking the gum when the layer has assumed a certain 

 consistency; when, in other words, it is sufficiently but not ex- 

 cessively smoked. On this consistency depends, on the one hand, 

 the good adhesion of this layer with that laid on over it; in 

 other words, the future quality of the gum. The time that is 

 taken to attain this consistency varies, according to the predeter- 

 mined dimensions of the ball and the fluidity of the given latex, 

 with the thickness of the stratum of latex (the seriugueiro can- 

 not always spread on the same quantity of latex) and with the 



temperature and composition of the smoke. The good workman 

 rapidly recognizes all these factors and works accordingly. The 

 adhesion among themselves of the various concentric layers 

 which form a ball and which we can detach by tearing off (which 

 constitutes, so to say, the commercial definition of "fine Para") 

 displays variations. This is due to the fact that the construction 

 of a ball is not effected at one time, and that between the various 

 stages of smoking there are intervals. If these intervals arc of 

 too long or too short duraticm the exterior layer — the last 

 coagulated— will have undergone modifications more or less se- 

 rious in its physical structure, inasmuch as these arc effected 

 spontaneously in time; the adhesion to the fresh coagulum which 

 forms the immediate upper layer depends on this physical struc- 

 ture, and will therefore vary more or less. 



.All these details have their importance in coagulation by smok- 

 ing as relates to the researches in the desire to industrialize this 

 process. What is sought is not only a certain coagulation but a 

 better ([Uality of rubber. To realize this quality, we ask our- 

 selves whether in reality a machine can replace human labor. 

 ,\nd then again, can it be claimed that coagulation by smoke 

 offers an economical advantage? Accomplished by one man it 

 recpiircs much time, an experienced handworker who is willing 

 to work in the midst of fumes, which, highly charged with anti- 

 septics, are injurious to the mucous membianes and the respira- 

 tory apparatus. 



Moreover, while smoking insures a certain uniformity in the 

 gum produced, it is, as a matter of fact, a very limited uniformity, 

 for it is confined not only to certain rubbers but even to the out- 

 put of certain scringueiros. This is due to multifarious causes 

 which would take too long to consider. This tends in the 

 meantime to sustain the opinion that coagulation by smoking is 

 not very simple or very easy to accomplish. 



On the whole, it is undeniable that coagulation by smoking 

 confers on the gum altogether superior qualities, and in seeking 

 the reasons we are reduced to hypotheses. As to knowing whether 

 there is an economical interest in generalizing the process by 

 mechanical means, experience alone can tell us what would be 

 the increased value of the product and what would be the cost of 

 treatment. But in the last few years these facts have been 

 placed in evidence, viz. : that the smoking machines invented in 

 Brazil are hardly- to be seen, except in museums, and have not 

 supplanted the ancient and primitive method, and that more 

 ])erfect macliines set up on some plantations in the Orient have 

 resulted in disappointments. Finally, it is in Indo-Malaysia that 

 the practice is spreading more and more of smoking the "sheets" 

 and "crepes" after coagulation, and in some instances the method 

 has furnished economically a product of very high quality. 



TWO RECE.N'T PATENTS FOR RfBBER CURINX DEVICES. 



In connection with the foregoing article, by M. Cayla, on latex 

 preparation by smoking, it may be of interest to note that a re- 

 cent issue of "Ceylon Observer" records a patent (No. 1312, dated 

 December 5, 1912) issued to Francis Alban Byrne, on "Improve- 

 ments relating to the coagulating and curing of rubber," in which 

 the inventor proposes to subject the latex to the vapors of sub- 

 stances obtained from the destructive distillation of wood, such 

 as wood-tar and (or) pyroligneous acid, heated in such a manner 

 as to effect their complete and quick volatilization, the fumes 

 thus created being brought by any convenient means into con- 

 tact with the latex. 



Another patent (No. 1352, dated June 14, 1913), issued to Leon- 

 ard Gastrell and Owen Dunbar de Vos, applies to a machine for 

 coagulating and curing rubber. The latex is contained in a 

 suitable receptacle and a revolving drum is brought in contact 

 with it so that a coating of late.x adheres to its surface. This 

 film of late.x is exposed to suitable smoke or fumes to effect its 

 curing, which is accomplished by a revolution of the drum in a 

 smoke chamber. The film of cured rubber being then detached, 

 the process is practically continuous. 



