Natural rubber

“ Common rubber is the prepared juice of a dozen or more shrubs and trees, all of which grow in tropical regions. [37] The belt of rubber-producing plants extends around [Pg 142] the world and includes such well-known species as the fig, the manihot (or manioc) , and the oleander; indeed, it is a condition of sap rather than a definite species of plant that produces rubber, and the latter is a manufactured rather than a natural product. The process of preparing the juice is practically the same in every part of the world. ”

“ The “Ule” rubber of Central America and British Honduras originates from Castilloa elastica. In S. America its natural occurrence appears to be limited to west of the Andes, but the tree is abundant in Mexico, Guatemala and Nicaragua. The rubber comes into commerce in thick strips or sheets or as “scrap.” The rubber is usually dark in colour and is often contaminated with proteid impurities derived from the latex. Ule rubber is generally inferior in strength to Para and commands a lower price. ”

“ The artificial production of rubber is not yet a matter of commercial interest. Dr. Gerlach, of Hanover, a practical manufacturer, thinks it may be twenty years before artificial, or, as it is sometimes called, synthetic rubber can compete with the natural. ”

“ The earliest experiment in cultivating rubber was made only as far back as the seventies of last century. And it is only within the present century that cultivated rubber, or, as it is more generally called, “plantation rubber,” has become a power in the industrial world. ”

“ The rubbers are heavier than the pacs and more protection to tender feet, but are more likely to tire the wearer, especially since rubber clings so fondly to all brush and weeds with which it comes in contact. ”

“ It should be remembered, however, that no rubber can be made strong enough to be absolutely proof against tearing or puncturing by extremely sharp edges, such as stiff stubble, sharp-edged rocks, broken glass, etc. ”

“ There are grounds for believing that raw rubber is superior in some respects to fully vulcanised rubber, if prepared without the addition of finely divided mineral substances which exert a toughening effect. ”

“ If the timber is too green, steam is formed as well as smoke, and the sheets of rubber may have a moist surface glaze.
Sun-Drying Sheet Rubber.—Among the first curious sights which impress the visitor or newcomer to this country is the spectacle of sheet rubber hanging in the sun on native holdings. From what one has learned of the extraordinary [148] care which must be exercised in all the processes of rubber preparation, one fails to understand how such rubber reaches the market without becoming tacky. ”

“ In spite of the wonders which rubber has already accomplished, and the adventures, which have colored its history, only the beginning of the romance of rubber has been told. The plantation industry is still in its infancy, and experiments are constantly being made to determine the best methods of planting, the most fruitful number of trees to the acre, the most advantageous way of tapping. In the laboratories of the great rubber manufacturers, scientists are at work improving old methods of using rubber and devising new ones. ”

“ Rubber is the name given to a coagulated milky juice obtained from many different trees, vines, and shrubs that grow on that part of the earth’s surface which forms a band some three or four hundred miles on either side of the equator. ”

“ The need of vulcanising in the process of manufacturing rubber goods became an axiom in pre-plantation days, and it is only quite recently that attempts have been made to utilise raw rubber directly, without vulcanisation, particularly for shoe soles. ”

“ On the other hand, rubber seems to cling to the ground, no matter how much it is worn. The only objection to rubbers is that they are uncomfortably warm in hot weather; but that difficulty can be overcome by frequently plunging into a cool stream and standing there for several minutes. ”

“ It will pay you to take some trouble to protect the rubber strands as far as possible. Lay them away in a can or jar in some cool, dry and dark place when they are not in use. Some boys cover the rubber with powdered chalk. When the surface of the rubber begins to granulate, its best days are over. Rubber is originally white in color, while the refining process gives it the familiar gray tone. ”

“ In the hospital the doctors use surgical instruments that have important parts made of rubber, and many of the patients are provided with rubber necessaries, such as elastic87 stockings, made of rubber thread, for bad legs, and false teeth on a plate of vulcanite, which is chiefly rubber. Travellers take rubber baths and rubber cushions about with them. Golfers play with rubber balls. Machinery would be at a standstill without rubber belting. What an inconvenient world this must have been to live in less than a hundred years ago, when anything made of rubber was a novelty! ”

“ At the most it is permissible to unite two or three layers of thin crepe to a thicker one by a single passage through even speed rollers, if the physical properties of the original rubber are to be conserved. ”

“ Plantation rubber can be very easily sampled and graded, because its form is such that it can be easily handled and seen through. But much of the wild product is sent to market in bulky masses. It is hard work cutting through the samples which are selected to undergo the test of seeing whether they are as good through and through as they are on the surface, or whether they contain any makeweight, such as bits of old iron or rope. ”

“ Air goods, such as cushions, beds, gas bags, and so forth, are made of textile fabrics which have been coated with mixed rubber either by the spreading process above described, or by means of heated rollers, the curing being then effected by steam heat. The manufacture of overshoes and fishing boots is an analogous process, only the canvas base is more thickly coated with a highly pigmented rubber of low quality. ”

“ Rubb′er-cloth, a fabric coated with caoutchouc; Rubb′er-dam, a sheet of caoutchouc used by dentists to keep saliva out of a tooth while being filled; Rubb′er-gauge, a device for measuring the amount of india-rubber needed to make a given article; Rubb′er-mould, a vulcanite mould used by dentists in shaping the plates for artificial teeth; Rubb′er-mount′ing, in saddlery, harness-mounting with vulcanite in imitation of leather-work.—n.pl. Rubb′ers, a disease in sheep, with great heat and itchiness.—ns. ”

“ A BALATA BLEEDERS’ CAMP. Page 47
From a photograph in the British Guiana Section of the Imperial Institute, by permission
In tapping a rubber-tree, the cut must only go deep enough to open the cells which harbour the sap—which, by the way, in simple English is called “milk,” and in technical language “latex.” These cells are in the bark, extending from just beneath its surface to the cambium, or true outer skin of the wood. If the tapping tool pierces the wood, the tree gets maimed for life. ”

“ The result was a flexible and durable cloth, but of great weight and thickness, and expensive to produce.
The chemistry of rubber is very little understood; as mentioned previously, rubber is a highly complex body, liable to go through many changes. These changes are likely to be greater in rubber varnish, consisting of half a dozen or more ingredients, than in the case of rubber alone. The action of sunlight has a powerful effect on rubber, much to its detriment, and appears to increase its tendency to oxidize. ”

“ Groups of botanists, chemists and arboriculturists study constantly tree diseases, methods of increasing the yield, and the other problems of growing fine trees that will produce high grade rubber. Here, by experiment and inspection, the secrets of the rubber tree are being brought to light, so much so that growers look to this plantation for leadership in methods of rubber culture. This great project so far from American soil and in a field so new gives a thrill of pride to the Americans visiting Sumatra on their way around the world. ”

“ India rubber can be so readily shaped in moulds and the latter are so readily made of plaster of paris that any one who is interested in such things will find endless amusement in working out different designs. ”

“ Rubber is a substance of so many important characteristics that its uses are countless. It is used for certain purposes because it stretches, for others because it is airtight and watertight, for others because it is a non-conductor of electricity, for others because it is shock-absorbing, and for others because it is adhesive. ”

“ Rubbers for large surfaces 23are usually made of soft old flannel, firmly and compactly put together somewhat in the form of a ball, and the more they possess softness and compactness, and are large and solid, the more quickly and satisfactorily will they polish extensive surfaces. Small pliable rubbers are usually employed for chairs or light frame-work. Perhaps for a beginner a rubber made of old flannel may be best, as it takes some little practice to obtain the necessary lightness of hand. ”

“ Nor are we impressed with the argument that, being rubber itself, it must be regarded as a material, and not an article composed of rubber, for its adaptation to dental purposes has differentiated it commercially. Washing and scouring wool do not make the resulting wool a manufacture of wool; cleaning and ginning cotton do not make the resulting cotton a manufacture of cotton; but sulphur and coloring matter, when applied as here, make the resulting rubber, while still remaining rubber, an article of rubber, as contradistinguished from rubber crude, or rubber merely cleansed of impurities. ”

“ According to the use to which rubber is to be put, it has to be mixed with certain other materials, to make a material that is neither too heavy nor too light, too hard nor too soft, too tough nor too elastic, to fulfil its purpose. And according to the price at which the goods are to be sold, certain other materials must be mixed with the rubber. It is with regard to the proportions in which such mixings are made that the manufacturers have secrets of their own which they specially want to guard. ”

“ While thus intractable by the usual methods, it is the most plastic of materials when properly treated. Its power of reproducing the finest details of a mould, of entering all the intricacies and undercuttings of a design, cause one to feel a peculiar pleasure in working with so responsive a material. ”

“ Where the scrap is removed from the edge of the bark on each occasion before tapping, the amount of rubber to be extracted from the dry shavings is very small—so small, in fact, that when the price of rubber is low, it is doubtful whether it pays to collect and work the material. ”

“ It is on rubber that infants cut their teeth; after all the teeth are gone old age makes use of rubber in plates for false teeth. Ten million motorists and other millions of cyclists in the United States ride on rubber tires that are durable, noiseless and airtight. Balloons of rubber float aloft, and huge submarines plow their routes beneath the ocean's surface propelled by electricity stored in great rubber cells. Sheathed in rubber, the lightning makes a peaceful way through our homes, offices and factories, furnishing light and telephone service. ”

“ Thus prepared, the skin is submitted to a strong pressure, which gives to it almost the hardness and elasticity which characterize the genuine whalebone, with the advantage that before or after the process of desiccation any color desired may be imparted to it by means of a dye bath.
349. Artificial India Rubber.—A man while experimenting recently with cottonseed oil for the production of a varnish, obtained to his surprise, not a varnish, but a rubber. By its use, with fifteen per cent. of genuine rubber, an article can be produced so exactly like the real as to defy detection. ”

“ Block rubber is considered to possess certain advantages in securing a constant proportion of water, and in being satisfactory for transport. The best condition and form in which to export rubber cannot be regarded as settled. The probabilities are that in the end the production of a rubber as nearly as possible free from water and impurities and of constant composition will be realized as best meeting the requirements of the modern manufacturer. ”

“ Many of the compositions which have been invented have been well adapted for use for certain purposes and have been used to adulterate the pure rubber, but no substance has been produced which could even approach India rubber in several of its important characteristics. There has never been a substance yet recommended as a substitute for rubber which possessed the extraordinary elasticity which makes it indispensable in the manufacture of so many articles of common use. ”

“ No matter how much synthetic rubber may be manufactured or how many rubber trees are set out there is no danger of glutting the market, for as the price falls the uses of rubber become more numerous. One can think of a thousand ways in which rubber could be used if it were only cheap enough. ”

“ The quality of rubber is almost impossible of determination by brief inspection or by chemical analysis. The relative amount of pure gum and of cheaper composition may vary, or good material may be injured by defective vulcanization. ”

“ It must be recognised also that the machines are liable to considerable damage if extraneous substances are allowed to enter—for example, tapping-knives, stones, pieces of iron, spouts, etc., which are sometimes present in the loose scraps of rubber or shavings, owing to the carelessness of coolies. ”

“ The word elastic, in physics, is the name given to the tendency which a body exerts, when distorted, to return to its original shape. Rubber possesses more elasticity than any other material known, it being possible to stretch a piece of rubber cord to eight or nine times its original length without fracture. Rubber also possesses the added requisite of lightness and will store up more energy than any form of steel spring. ”