Open main menu

Once a Week (magazine)/Series 1/Volume 9/"Silvertown"

< Once a Week (magazine)‎ | Series 1‎ | Volume 9




The boy's most popular notion connected with india-rubber is, that it is good to make "bladder pop;" and in order to make this material, it has to go through a process of manufacture which comes to boys by a kind of instinct. We all remember during "map days," how the india-rubber, too often called into requisition, grew hot and crumbled, and as the pieces broke off, how they found their way into the mouth to undergo the process of mastication, and how, when chewed to a proper consistency, it became ductile, non-elastic, and sticky,—qualities requisite to make it imprison the air, which, on pressure, forced its way through the yielding substance in the shape of bladders, that burst with a pop, the sole reward of the school-boy for hours of very tiring jaw-work. How little we imagined, when employed in this manner, and enjoying by anticipation the simple pleasures of the final pop, that we were going through a process which science has since indicated as the best method of manipulating india-rubber for the purposes of the domestic arts. In the powerful machinery employed by the manufacturers of caoutchouc, we see but an elaboration of the masticating powers of the boy's jaw, which, with the heat of the mouth, works up the sixpenny square of india-rubber into the substance we are all so well acquainted with.

We paid a visit, the other day, to "Silvertown," the little manufacturing village at North Woolwich, belonging to the Messrs. Silver, in which the many substances into which india-rubber can be transformed are produced by the powerful and curious machinery there at work; and it was whilst watching the different processes, that we came to the conclusion, that the boy is father to the man, even in a manufacturing capacity, as we have already hinted.

How little we are able to forecast the uses to which a new material may ultimately be applied, is perhaps as much evidenced by this substance, Caoutchouc, as by any other in existence. As far back as the year 1770, Dr. Priestley, in the introduction to his book on Perspective, says, "Since this work was printed off, I have seen a substance excellently adapted to the purpose of wiping from paper the marks of a black-lead pencil. It must therefore be of singular use to those who practise drawing. It is sold by Mr. Maine, mathematical instrument maker, opposite the Royal Exchange. He sells a cubical piece of about half an-inch for three shillings, and he says it will last for several years."

How little this philosopher imagined that a substance thus incidentally mentioned in a drawing-book, was destined to become one of the most useful substances in the arts and sciences—nay, to be an absolute necessity of civilisation.

It is, at the same time, very remarkable that, for upwards of sixty years, india-rubber never advanced beyond the hands of the drawing-master, and that, during that long period, all its virtues were supposed to consist in its power of correcting school-girls' drawings. How many substances are there still before the world in a like condition of embryo?—what is to be the splendid future of gutta-percha, aluminum, and the other scores of new substances that are beginning to "crop" up around us?

It would seem as though it were destined for the rubber plant to play a great part in the world, as it is found in great abundance in all parts of the globe, within tropical latitudes; and, like the palm, it is probably destined to do the missionary work of civilisation far more effectually than any of our societies constituted for that purpose, as the pursuit of these two valuable products will lead organised bands of European traders deeper and deeper into the recesses of the tropical wilderness—where the solitary missionary could not hope to make any permanent lodgement. The best kinds of caoutchouc are the Para and the bottle india-rubber, the latter is familiar enough to the reader: but perhaps it is not so well known that what is termed caoutchouc is the milk sap of trees, and that this juice is to be found in many other trees besides the rubber tree; indeed, there seems to be little doubt that we may draw upon a large portion of the tropical vegetable world for this valuable material. The india-rubber as imported takes the form of bottles, and there is a kind known as negro-head, possibly because when cut open it presents an appearance somewhat like that of a human brain, with its numerous convolutions. The first process we witnessed at the Messrs. Silver's was the softening of these bottles and "negro brains," if we may use the term, in a large tank, filled with warm water. The rubber is macerated here for some hours, for the purpose of softening and cleansing it—the process it undergoes in the school-boy's mouth. When it has been long enough in the water, it is taken to the masticating machine, which is a kind of calendering apparatus, heated by steam, and operating upon the lumps of rubber as the boy's grinders do. You see the big lumps drawn in between the smooth cylinders, apparently the most obstinate, indigestible, unmanageable stuff in the world, and after a while it issues from the other side in the form of so many "brown bread towels," or those coarse-looking, oatmeal coloured rubbing cloths that are a necessary appendage to every sponging-bath. The transformation from the dirty-looking lumps of rubber to these little towels, about eight inches wide and three feet long, is the oddest thing possible. As they emerge, they are folded up and placed on shelves, just as we see them in baths and wash-houses. Twenty-four hours' exposure to the air changes their oatmeal colour to a very dark brown. This is the first stage through which all the different preparations of india-rubber go—its cleansing process. The reader will possibly remember that india-rubber presents itself under different aspects, either as pure india-rubber, such as tobacco-pouches, &c., are made of, or as whitish-looking india-rubber, which we are familiar with in the form of macintosh cloaks. The vulcanised india-rubber has a somewhat similar aspect—a clay-like colour, as far removed as possible from the rubber as we see it in the bottle. Pure india-rubber is manufactured in a very simple manner. A number of the brown bread towels are taken to the masticator, a machine composed of two powerful steel rollers, revolving with unequal velocities, and heated by steam. The "towels" disappear in this powerful mangle, and the act of masticating begins. As towel after towel disappears, the rubber is worked into a huge bolster, which is masticated over and over again, until it assumes the form of sticky pulp—"bladder pop," in fact, on a large scale. The bolster is now taken from the machine, and placed in an hydraulic press, one foot wide, nine inches deep, and six feet long. Here it remains for two days, under a pressure of fifty tons, and comes out a solid block of homogeneous india-rubber, big enough for a Titanic drawing-master. It has now to be cut into sheets. This is done by placing it in a machine fitted with a cutter, which cuts with a quick lateral or saw-like motion. The block is pushed forward against this cutter, and the thickness of the sheet can be regulated to the hundred and twentieth of an inch; indeed, sheets of that tenuity are sometimes made. It is a pretty sight to watch the thin film of rubber being detached in this way, with an unerring accuracy.

The most important application of india-rubber in this form, is its use as an insulator for telegraphic purposes. Hitherto, gutta-percha has been almost universally employed—for deep-sea cables especially—but there can be little doubt that india-rubber is a far more durable material, and it is slowly coming into use, notwithstanding the opposition of the manufacturers who have embarked large capital in the collection and working of gutta-percha. It is one of the most interesting sights in the manufactory to see the machinery envelope the telegraphic wires with its non-conducting rubber sheathing. This is done by winding round them spirally thin bands of rubber, by machinery driven by steam-power. Thirty or forty spindles for this purpose are seen revolving in a large room, and hundreds of miles of wire are thus covered in the course of the week. The covered wire is subjected afterwards to heat, which fuses the laps of the covering riband of rubber together, and thus makes it impermeable to the entrance of water, and effectually prevents the escape of electricity.

The process of manufacturing soft india-rubber is more elaborate. What is termed Spread sheet india-rubber, or that kind of which waterproof garments are manufactured, is made by masticating, and mixing sulphur in the proportion of two ounces to a pound of the rubber, and then dissolving it to the consistency of dough by the admixture of naphtha. When in this soft state it is passed through finely-adjusted rollers and spread out into thin sheets; these as they emerge from the rollers or rolling-pins,—for the rubber is spread out like so much dough,—are passed over a steam chest, which drives off the naphtha and dries, to a certain extent, the material. In some cases the film is rolled on to a cotton fabric and adheres to it, film after film being added until it is built up to the required substance: the object of this building up being to prevent the possibility of airholes occuring, which would be fatal to a waterproof or air-proof material. When it is not necessary for the india-rubber to be lined with cloth, the roller of that material on to which it is wound, is sized, consequently no adhesion takes place between the two materials, and the rubber is easily peeled off. The process of Vulcanisation that gives such extraordinary resiliency to the material, which we are so familiar with in the form of india-rubber bands, springs, &c., is accomplished by the application of heat. The sulphur having already been worked into the material and thoroughly incorporated with it, the articles made of this hard compound are carefully packed in sand so as not to touch one another, and then are run into steam chests, where they remain from two to six hours, according to thickness, at a heat varying from 200 to 300 degrees. This application of heat turns the soft doughy substance into the famous elastic material which, under the name of vulcanised india-rubber, is even invading the province of steel in the manufacture of springs. What is the nature of the chemical change which takes place when this final increment of heat is applied, is entirely unknown, and the discovery itself was one of those fortunate accidents which have so often produced noble fruit. The peculiarity of the elasticity produced by vulcanisation is, that its power never seems to be worn out. The bow must be unbent, if its force is to be husbanded, but an india-rubber band may be kept stretched to its utmost limit for years, and it will still retain its wonderful resiliency.

But we have yet to describe another process—that of manufacturing Hard india-rubber. To Goodyear, the American, the merit of this great discovery is due, for great we must call it, inasmuch as it has introduced into the arts and sciences a material somewhat similar to horn, but which possesses qualities far surpassing that natural product, and which can be made in any quantities and in any sizes.

In this new material a very large amount of sulphur is used; to produce mere vulcanisation two ounces to the pound of rubber is sufficient, but to make hard india-rubber or ebonite, as the Messrs. Silver term their preparation of it, as much as two of sulphur to one of rubber is used. The application of great heat, say 300 degrees, transforms the india-rubber thus treated into a material more resembling to the eye ebony than anything else—a dense black substance, which takes a high polish, is very light, and to some slight extent elastic. The uses to which hard indiarubber is put can scarcely be enumerated. In many articles it is entirely displacing horn and tortoiseshell. Hundreds of tons, for instance, are sold to the comb makers ; for paper-knives, handles of all kinds, bracelets most closely imitating jet—but with this advantage over that material, that it will not break by falling on the floor—cups and troughs of all kinds, and especially those for the use of photographers, as neither acids nor metals have action upon it; in short, we scarcely know to what this beautiful hard substance is inapplicable, so multifarious are the uses to which it has already been applied. It is greatly used as an insulator in telegraphy, in consequence of its non-conducting quality; and moulded into forms before being baked, it takes the place of many articles formerly made of gutta-percha, to which material it is infinitely preferable, as it is neither affected by heat nor cold.

The little community of Silvertown is, as it were, self-contained. Situated, as it is, far away from the town, on the Essex shore of the Thames, the proprietors had, as it were, to found a little colony. When the factory was built, there were no houses near, and no market, consequently the Messrs. Silver had to provide for the wants of their work-people, and they certainly have done so with a care worthy of all praise. The rows of cottages in which many of their work-people are housed contrast very favourably with the squalid habitations one passes on the railway in going to the factory. Then there is a store in which bacon, flour, and many othcr necessaries of life, are obtainable at cost price, and a public-house in which the beer is pure. The Messrs. Silver found it was incumbent upon them to build a public-house, otherwise it would have been done for them by independent parties, and the consequence would have been that, a very efficient means of administering to the comfort of the work-people, and at the same time of controlling excess, would have passed out of their hands.

The great charge brought against the manufacturers, as a class, used to be that they were utterly careless with respect to their "hands," and that they looked upon them merely as machines—or rather less than machines—for when their day's task was done, they washed their hands of them, and cared not what became of them; a state of things which placed the free Englishman, as regards physical comfort, in a less favourable position than the negroes, whose bodily wants their masters have always had the good policy to attend to. In thus making themselves responsible to a certain extent for the domestic comfort of their work-people, the employers are doing service to the community at large, for it is to the exertions of individual manufacturers that society must look for the accomplishment of that all-important task, the elevation of the social status of the workman. The example of little communities such as Silvertown is beginning to tell upon that mass of squalor which once seemed to be so hopeless in its immensity. It is becoming a habit of large manufacturing companies, we are happy to see, to look upon their workmen as human beings, to be cared for, as well as machines, to be used up; and the formation of the two little colonies of engineers at Wolverton and Swindon has been followed on a smaller scale by thousands of private employers throughout the country, who have found out that their own interests are concerned in concerning themselves with the happiness of those in their employ. The Messrs. Silver may justly pride themselves in belonging to the noble brotherhood of scientific men which is doing such good service to the commonwealth. A. W.