Gutta Percha , (Malay, gutta, gum, and percha, the name of a tree), an inspissated juice called gutta taban by the Malays, the name being misapplied by the English. The tree which produces the gum was referred by Sir W. J. Hooker in 1847 to the natural order sapotaceoe and Dr. Wight's new genus isonandra, and named the isonandra gutta. It was formerly abundant in the forests along the foot of the hills in the Malayan peninsula, but the natives by cutting down the trees to procure the juice exterminated the plant, and the supply now comes from Borneo and other islands of the Indian archipelago. It is a large tree, commonly 3 to 4, but sometimes 6 ft. in diameter, with a straight trunk and reaching the height of 60 or 70 ft. The branches are numerous and ascending, and crowded with leaves at their extremities; these are petiolate, oblong, 4 or 5 in. long and 2 wide, of bright green above and brownish beneath. The flowers are small and white. The wood is peculiarly soft, fibrous, and spongy, pale colored, and traversed by longitudinal receptacles filled with the gum, forming ebony-black lines. To the Malays the valuable properties of the juice of the tree were known long before the Europeans became acquainted with the article.
The natives found that the gum would become soft and plastic in hot water, and, being then moulded into any form, would retain this when cold. They made it into basins, vases, shoes, elastic sticks, whips, handles for parangs or axes, etc. The attention of Europeans was first called to it in 1842 by Dr. William Montgomerie, assistant surgeon to the residency at Singapore; and in 1843 Dr. D'Almeida of the same place brought specimens of the gum to England and laid them before the royal Asiatic society. They attracted little attention till further communications from Dr. Montgomerie established the importance of the article by showing its applicability to the same uses as caoutchouc, and to others besides, and also the low cost at which the material could bo procured in the greatest abundance. In 1844 a shipment of 2 cwt. was made from Singapore as an experiment, and soon after the product suddenly became a commercial article of importance. In 1847 Dr. Oxley published an interesting account of the tree and its product in a Singapore journal, describing the uses to which he had applied the gum for surgical instruments.
He stated that the large trees winch were formerly very abundant on the island of Singapore had been nearly all cut down by the natives, who adopted this destructive method of obtaining the juice, and who had sacrificed by his estimation G9,-180 trees to procure one tenth this number of piculs, which was the exportation from Jan. 1, 1845, to July, 1847. The custom of tapping has since been introduced. The sap soon coagulates after it is collected, or it is made to do so by boiling, and is then kneaded by hand into oblong masses, 7 to 12 in. long and 4 or 5 broad. Its dark reddish brown color is derived from the impurities, as bits of the bark, that have accidentally fallen into the juice, or from sawdust and other substances introduced as adulterants. - Rarefied gutta percha has a brownish red color and a density of 0.979. It is a non-conductor of electricity, and by friction with almost any other substance (gun cotton and collodion are exceptions) it develops negative electricity. At ordinary temperatures it has considerable tenacity, being nearly as strong as leather, but much less flexible. When heated to 115° F. it becomes pasty, and between this and 140° or 150° it may be moulded into vari-ous shapes or drawn out into wires or tubes.
It is insoluble in water, and slightly soluble in anhydrous alcohol and anhydrous ether, but soluble in boiling olive oil, from which it is deposited on cooling. Benzine, sulphide of carbon, chloroform, and oil of turpentine dissolve it with the aid of heat. It is insoluble in alkaline solutions or hydrochloric and hydrofluoric acids, and therefore may be advantageously used as a material for vessels to contain these liquids. Strong sulphuric acid carbonizes it, and nitric acid oxidizes it, converting it to a yellow resin. Gutta percha is remarkably porous. If a thin film be deposited upon a plate of glass or porcelain from its solution in sulphide of carbon, when examined with the microscope it will be found full of minute pores. When subjected to traction it becomes fibrous, and will then resist a much greater force without extension. Pure gutta percha is a hydrocarbon, having the formula C20II32. When exposed to light and air it slowly absorbs oxygen, and is converted into a white resin, having the composition C20H32O2, and a yellow, C20H32O2 both of which are soluble in boiling alcohol.
The purified commercial article usually contains from 75 to 82 per cent. of pure gutta, the remainder being composed of the two resins just mentioned. - The treatment of gutta percha is similar to that already described under Caoutchouc. The first process is to purify it of the foreign substances, as earth, stones, and sticks, with which it is contaminated. For this purpose the blocks are sliced, by knives attached to powerful wheels, into shavings. These are introduced into a large tank of water heated by escape steam to boiling. The gum softens and runs together, and by the boiling most of the impurities separate and subside. The mass is then removed to a machine called a teaser, which is a large box containing a drum armed with rows of crooked teeth. This, revolving rapidly, tears the gum into shreds, which fall into a vessel of water, in which it floats, and the remaining impurities subside. The purified fragments are again boiled; they again run into a soft mass, and this is taken into the kneading or masticating machine, which is a strong cast-iron box containing a revolving cast-iron drum armed with strong iron teeth; or instead of the drum, two parallel rollers with screws on their surface are employed.
Steam is let into the machine, and the gutta percha, kept soft by its heat, is thoroughly kneaded and brought to uniform consistency without air or water in the mass. It is then ready to be rolled into sheets or pressed into tubes; the former in their various sizes and thicknesses furnish the article in shapes convenient of application to most of the uses to which it is adapted. Tubes are produced by forcing the kneaded mass through a steel cylinder which terminates in a mould with a circular metallic core. Passing through this, the soft substance is prevented from collapsing by being drawn through a long channel of water by the revolution of a drum at the other extremity of the canal. By continually supplying the material the tubes are made without interruption; and in this way a single length has been produced of 1,000 ft. These tubes by their remarkable strength are well adapted for resisting great pressures; they are used for aqueducts, for feed pipes of steam engines, for hose, pump barrels, and various other purposes connected with the conveyance of water, gases, and vapors.
The first machinery built for the coating of telegraph wire with gutta percha was in the autumn of 1848, at the works of the American gutta percha company in Brooklyn. The first order for the prepared wire was for the Morse telegraph company, and it was laid across the Hudson river at Fort Lee in August, 18-1-9. The gutta percha employed was prepared with the greatest care to insure its purity. The raspings, rolled and then macerated in hot water, were washed in cold water, and then, being softened by boiling water, were driven by hydraulic apparatus through cylinders, in the end of which were wire-gauze sieves. After this the substance was thoroughly masticated and kneaded, by which it was entirely deprived of moisture and rendered homogeneous and compact; and it was then introduced into the long horizontal cylinders kept hot by steam, and powerfully compressed by screw pistons worked by machinery. As it was forced out at the extremity the gutta percha was made to pass through a die, in which the strand of copper wires was introduced, and the whole was drawn along by a revolving drum upon which it was wound. A second and third layer of gutta percha were added to the core by repetitions of the process.
Mr. Charles Goodyear applied the same process to moulding various articles in gutta percha, attaching the moulds, which were of metal in several pieces securely bolted together, to the end of the cylinder, through which the plastic gum was forced. Holes were left for the escape of the air in the moulds, and the appearance of the gutta percha at these indicated the completion of the filling. - Gutta percha is often used in combination with caoutchouc, the latter serving to soften and render the material more pliable and elastic, and less liable to be affected by changes of temperature. Both are alike affected by the treatment called vulcanizing, which is thoroughly mixing the gum with sulphur or some of its compounds, and then subjecting the mixture to an elevated temperature in close vessels. (See Caoutchouc.) The methods and materials employed for vulcanizing gutta percha are numerous, and the object desired is not always the same. A hard horny material is produced under the patent of Mr. Stephen Moulton, by mixing the gum with hyposulphite of lead and adding more or less of calcined magnesia, and then subjecting the compound to a temperature of 250° to 300° for some hours.
Mr. Hancock in his patent of 1847 employed a mixture of 48 parts of gutta percha with 6 parts of sulphuret of antimony, sulphu-ret of calcium, or some other similar sulphuret, and 1 part of sulphur. Mr. Emory Rider of London in 1856 patented an improvement which consisted in the addition of 1 part of litharge to 66 parts of gutta percha, together with 1 part of sulphur, or its equivalent in some of its compounds. These substances are mixed and well incorporated into the plastic gum by the action of heated rollers, which, revolving at different speeds, powerfully wear and grind the material; after which, in a close metallic vessel one third filled, it is subjected to the vulcanizing temperature for a few hours. The patents for mixing gutta percha with other substances are too numerous to be particularly noticed; even these substances are almost innumerable. The object of these various mixtures is to produce materials of different degrees of hardness and of different capacities of resistance to changes of temperature and other causes of change, but which may still be moulded into and retain the form of useful articles. The principal use of gutta percha is for covering telegraph cables.
It is also used by dentists for taking impressions of the teeth and gums, and sometimes for a temporary filling for cavities. Baths and other articles for chemical laboratories, as funnels and tubing, may also be advantageously made of it. Many articles sold under the name of gutta percha are compositions of caoutchouc with other substances.
Gutta Percha (Isonandra gutta).