HANCOCK ' S ORIGIN AND PROGRESS OF INDIA-RUBBER MANUFACTURE. * THERE may be
in this volume rather too much of the air of a trade circular, and, as the author admits' an appearance of egotism, caused by the continual introduction of his own experiments and inventions. The "narrative," however, is a curious account of the rise and progress of a very important manufacture, employed on a material that, originally looked upon as little better than a curiosity, or at most as "India-rubber," has now become extended to many of the conveniences of life. The book is further curious as another illustration of the seemingly trifling difficulties that practically impede an invention' and the seemingly trifling causes that remove them when the true principle and the mode of applying it are discovered. The two great properties of caoutchoue, that adapt it to so many purposes, arc elasticity and impermeability ; the elasticity extending from the wrist-spring of a glove up to the buffer of a railwaycarriage' which is to diminish the shock of a train ; the impermeability from a water-proof cape or a pair of goloshes to a pontoon or a boat. These two properties were separately developed by Mr. Hancock, the author of this volume, and his subsequent partner, Mr. Macintosh, who has given his name to so many articles." In 1819, Mr. Hancock, 'with some knowledge of mechanics but little of chemistry, began to experimentalize on India-rubber, with definite views ; and in 1820 he took out his first patent for the application of the elasticity of India-rubber to gloves, waistcoats, stocks, and a variety of other purposes, chiefly connected. with dress. Much about the time that Mr. Hancock began his experiments, the late Mr. Macintosh was extensively. engaged at Glasgow in some chemical manufactures that yielded in the result a quantity of naphtha; and "the thought occurred to him of its being possible to render this useful from its powers as a solvent of caoutchoue." Experiments succeeded ; a strong water-proof varnish was the result ; and in 1823 Mr. Macintosh obtained a patent for the discovery, and established his water-proof manufacture at Glasgow, which he afterwards removed to Manchester.
It does not seem that either the elastic or the impenetrable branches of business had many external difficulties. They were as fairly patronized as a new invention could expect to be ; they do not appear to have been troubled with interloping rivals at the outset. Mr. Hancock, however, met with obstacles of his own in the smallest matter he attempted ; and one of them originated in a way which often beset him—sewing.
"The India-rubber springs must of course be attached in some way to the article to be elasticated, and women were set to work to sew them in with needle and thread ; but after they had been a short time in use, I found the holes made by the needles so many tearing-places, and also that if a needle was passed-through any part of the rubber it endangered a fracture. To remedy this in some measure, I made the ends of the springs much thicker and wider than the central parts, so that the weaker part • Personal Narratice of the Origin and Progress of the Caoulehoue or IndiaRubber Manufacture us .England. By Thomas Hancock. 'With Engravings. Ti, which is added, some Account of the Plants from which Caoutchouc is obtained, Re. Re. With an Appendix containing a Specification of the Author's Patents. Published by Longman and Co.
yielded its elasticity sufficiently 'without bringing much strain upon the thick ends, where the punctures of the needle were made. But the neces sity for this form of spring brought other difficulties : instead of cutting in straight lines, each spring had to be hollowed out, tapering on both sides and both edges, and contrivances had to be adopted for this purpose. The needle-holes did not then tear out. I soon found that the knives and cut ting-tools required to be kept wet with water. These springs, however, had not long been in use before they were returned in numbers broken. By pulling out new springs smartly and allowing them to return quickly, I
observed, after a time that the angles became finely serrated like a saw, and each nick increased in size as I followed up the operation, until the spring snapped in two. This appeared to be a very formidable obstacle to success as regarded springs, but was soon overcome, for I observed that some of the new springs were and some were not affected in this way ; and on tracing hack the steps that had been taken with the two kinds, I found that those springs on which I had used boiling water, after they were cut, did not crack on the edges and I had no further trouble on this score, always taking care in all future cases, when edges were freshly cut, to give them a hot bath.
"This discovery was of great value to me, as furnishing the fact, at this early period, of the great importance of employing heat in treating this substance ; as will be seen throughout the progress of its future manufacture."
The process of making the ends of the springs wider and thicker induced waste. This, with the then scarcity of the material, and the uncouth forms in which it was frequently imported, rendered
it necessary to discover some plan of uniting pieces of Indiarubber together on a large scale. Mr. Hancock knew by experiment that fresh-cut edges of India-rubber joined readily ; but after exposure they would not unite at all. He fried various plans) with imperfect success. At last he contrived, a machine, in principle not very unlike the ra-cutting machine of the papermanufacture—a cylinder armed with teeth shut up in a box. His object was to tear the pieces of India-rubber into tatters, and then by means of heat and pressure unite them. When all was prepared, the India-rubber for experiment was put in, and the cylinder turned by means of a winch. "The teeth began to operate, and it soon became evident that some action was going on inside that I had not reckoned upon, as much greater power became necessary to turn the winch. After turning some time, the hole at the top of the hollow cylinder was opened, and presently, to my great surprise, came out a round solid ball. This ball, when cut open, presented a marbled or grained appearance ; the union of the pieces was complete; the graining exhibited the pieces curiously joined together, the exterior surface of them having been acted upon so as apparently to alter their condition, whilst the interior portion of the pieces seemed to be in the same condition as when put in. The ball was replaced and the action was continued for a long time, and when taken out again it had become very hot ; and on cutting it open all the graining had disappeared ; the whole had become a solid homogeneous mass."
As the application extended to a greater number of articles, obstacles arose from the prejudices of interest and habit. When water-pipes or hose were manufactured the in oks"
article etuud stoutly up ior notnmg uke matler. either pre': judice or bribes induced the firemen, brewer's men, dm., to vote against caoutchouc. The St. Crispin mind could not be got to overcome the absence of "awl and bristles." The greatest difficulty was with the tailors : they could, not in those days away with a loose fit and little stitching. "I should mention here, that neither the firm nor myself [there was now a connexion between Hancock and Macintosh] ever intended to have any retail-shops' and we desired by all means to avoid the making of garments, and wished to sell our goods only in a warehouse but we were compelled to do all three, or lose our business. Some—most:—of the tailors set their garments were not water-proof; at every seam, the cloth, being necessarily faces against the use of our material ; others made it utgo badly that the punctured by the needle, allowed the water to pass. Our advice was to make no close garments, and as few seams as possible ; and to enable them to do this, we furnished the cloths wide enough to make the length of cloaks and capes : but they persisted in making garments to sit close, and were greatly offended when told that they could not sew a water-tight seam, and that it was necessary to send their garments to us to have the seams lined to make them proof. Some of them persisted, and actually made a double row of stitches, to make sure work of it! We tired of all this, and opened retailshops, and employed our own tailors, and proofed our seams; and even then, so accustomed were these men to pin their work, that we very frequently found pin and needle holes in the body of the cloth."
Other troubles arose and were overcome ; nor has caoutehouc in some of its forms been free from the caprice of fashion or the change of circumstances ; railways having at first lessened the demand for water-proof wrappers. A great difficulty always felt was in the susceptibility of the substance to temperature, hardening in cold, softening and becoming clammy in warmth. From specimens brought to England in 1840, some American would seem to have discovered a remedy, but nothing came of it, nor was more heard of it. About 1842-'43, Mr. Hancock was engaged upon some experiments for divesting rubber of its adhesiveness ; improving the colours artificially imparted to it, &c. He therefore determined to extend his experiments to the matter of temperature. These occupied him a long time, somewhat after the groping fashion of Palissy the Potter. It is probable that a regular chemical education might not have directly aided him ; for now that the discovery is made it cannot be accounted for. Knowledge would perhaps have shortened his labours by enabling him to have conducted them more systematically, as it would certainly have induced a more regular account of his experiments. However, he found that placing India-rubber in a hot sulphur bath hardened it to almost any degree, without depriving it of its useful roperties. Professor Brande, in a lecture, has so neatly stated the whole results, that we will present them in his words.
"If we expose this mixture of rubber and sulphur for a due time to a high temperature, which may vary with Circumstances, a Change ensues. here heat it to about 300', and find the characters of the rubber gradually alter. Ultimately it will be changed or vulcanized' that is, it will have acquired the new characters and properties to which I have briefly alluded. Its elas ticity is not only increased, but is now not affected by change of temperature; that is, it is not in the least hardened or altered by any degree of cold ; it retains its perfect elasticity at the lowest temperatures; and what is perhap% even still more remarkable, when heated it does not fuse and become clammy and viscid, but remains unchanged at all temperatures short of its absolute decomposition ; ether, oil of turpentine, naphtha, and its other solvents, now barely affect it ; oil and grease no longer penetrate and soften it. Such are the new properties conferred upon the rubber by the joint operation of sulphur and heat; it is now said to be vulcanized. But the most curious part of the story remains to be told, and arises out of this question, namely, What quantity of the sulphur is required to be thus combined with the rubber for the purpose of changing it? Certainly not more than one or two per cent ; for if by any of the solvents of sulphur, as for instance by the alkalies, I remove all excess of sulphur, I in no way affect the new properties; but yet further, if I take steps still to remove more of the sulphur, and ultimately leave the rubber apparently quite free from it, I still find that it retains all those peculiarities which 1 have enumerated as characterizing vulcanization. May we not therefore conclude, that, under the Will-. ence of sulphur and heat, the rubber acquires its new and distinct properties, not by actual chemical combination with a minute portion of sulphur, but by the assumption of a new molcerdar condition; that, like phosphorus, it has assumed an allotropic state. In short, these allotropic conditions of bodies are daily becoming more worthy of remark and inquiry : thus, it is not unlikely that steel even may be an allotropic condition of iron, produced under the influence of carbon upon iron at high temperatures, for the quantity of carbon in the finest steel does not reach one per cent ; and there are cases in which the metal is nearly pure to all chemical tests, and yet retains the leading characters belonging to steel."
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