Rubber Hand Stamps and the Manipulation of Rubber
9781465667663
213 pages
Library of Alexandria
Overview
India rubber or caoutchouc is a very peculiar product, which is found in and extracted from the juice of certain trees and shrubs. These are quite numerous and are referred for the most part to the following families: Euphorbiaceæd, Urticaceæd, Artocarpeæd, Asclepiadaceæd, and Cinchonaceæd. It is evident that a considerable number of trees are utilized in commerce for its production, and it is certain that it exists, quite widely distributed, in many cases as a constituent of the juice of plants not recognized as containing it. When an india rubber tree is tapped, which is effected by making incisions in the bark, the sap of the tree exudes. It is a milky substance and is collected in various ways; it may be in vessels of clay, in shells, or in other receptacles by the india rubber hunters. If this substance is examined it is found to be of very remarkable and characteristic constitution, resembling in its physical features ordinary milk. It is composed of from fifty to ninety per cent. of water, in which is suspended in microscopic globules, like the cream in milk, the desired caoutchouc or india rubber. If the juice is left to stand in vessels, like milk in a creamery, the globules rise to the surface, and a cream of india rubber can be skimmed off from the surface. If the juice is evaporated over a fire, the water escapes and the india rubber remains. By dipping an article repeatedly in the juice and drying it, a thick or thin coating of india rubber can be developed. Before the modern methods for the manipulation of the gum had been developed, and before the invention of vulcanization, this method was adopted for the manufacture of shoes. The original “india rubbers” for protection of the feet in wet weather were made in this manner. A clay last was used, upon which the india rubber was deposited as described. The clay last was then broken out and removed. Great quantities of overshoes were thus made in South America, and many were exported to Europe. When caoutchouc has once been removed from this watery emulsion, which for all practical purposes is a solution, it cannot be restored to the former state of liquidity; it remains solid. It will absorb a considerable quantity of water, but will not enter again into the quasi solution or combination. This property of permanent coagulation, which interferes to a degree with its easy manipulation, was early discovered. In the last century quantities of the natural milk were exported to Europe to be used in what may be termed the natural process of manufacture, because once solidified it could not be redissolved, and because the manufacturers of those days had not the present methods of dealing with the apparently intractable gum. The natives of South America before the advent of Europeans, were familiar with the treatment of the juice by evaporation just described and used to make bottles, shoes and syringes of it for their own use. The name Siphonia applied to several species of rubber tree, and seringa (caoutchouc) and seringari(caoutchouc gatherer) in Spanish recall the old Indian syringes and tubes.
