Part 87

Inner tubes for pneumatic tires may be classed under three headings, according to the methods used in their manufacture, viz., seamed tubes, rolled tubes, and tube-machine tubes. By far the greater number of tubes come under the first two headings. For seamed tubes, the rubber is taken from the calender in the form of sheets from one-sixteenth to three-sixteenths of an inch in thickness. These sheets are cut into strips of proper length and just wide enough to make a tube of proper cross-section diameter when the two long edges are folded over and fastened together with rubber cement. These two long edges are cut on a bevel so that they make a good lap seam. The tube is then pulled over a mandrel of proper size and a thin piece of wet cloth rolled around it, and then it is spirally cross-wrapped with a long, narrow piece of wet duck for its entire length. The whole is then put into a regular heater and the tube vulcanized. After vulcanizing the wrapping is removed and the tube stripped from the mandrel, turning the tube inside out, so that the smooth side which is vulcanized next to the mandrel appears outside, and the rough side showing the marks of the cross-wrapping is inside. The valve hole is then punched in the tube, the valve inserted and the open ends of the tube buffed down to a feather edge. The tube in this state passes to the splicers, who cement the buffed ends and splice them together, placing one open end within the other, making a lapped seam around the tube about 2¹⁄₂ inches long. The cement used in splicing is generally cured by an acid which chemically vulcanizes the rubber without the application of heat. The tube is thus finished and ready for the market. Rolled tubes are made from very thin sheet rubber by rolling same over a mandrel of proper size, until the required number of layers of thin rubber have been rolled on to give the tube the desired thickness. The tube is then wrapped, cured and spliced, in exactly the same manner as a seamed tube.

What Is Rubber?

Crude rubber is a vegetable product gathered from certain species of trees, shrubs, vines and roots. Its characteristic peculiarities were early recognized by the natives of the tropical countries in which it is found. Records of the earliest travelers in these countries show that the natives had used various articles, such as receptacles, ties, clubs, etc., made from rubber, but it was not until about 1735 that rubber was first introduced into Europe. In civilization rubber was first used for pencil erasers and in waterproof cloth, and finally in cements. Vulcanizing, or the curing of rubber, was not discovered until 1844, and thereafter the development of the rubber industry was very rapid, especially in Great Britain.

There are many kinds and grades of rubber, and to-day these can be divided into two chief classes, wild and cultivated.

Gathering Rubber in South America.]

Pictures herewith by courtesy of The B. F. Goodrich Company, Ltd.

What Is Wild Rubber?

~WHERE RUBBER COMES FROM~

The first class, or wild rubbers, are collected from trees which have grown wild and where no cultivation processes whatsoever have been used. These rubber-producing trees, shrubs, etc., are found mostly in Northern South America, Central America, Mexico, Central Africa and Borneo.

The finest rubber in the world is Fine Para, and is gathered in the Amazon regions of South America. This rubber has been gathered in practically the same way for over a century. The natives go out into the forests and, selecting a rubber tree, cut “V”-shaped grooves in the bark with a special knife made for the purpose, these grooves being cut in herring-bone fashion diagonally around the tree, with one main groove cut vertically down the center like the main vein in a leaf. The latex, or milk-like liquid, of the tree, from which the rubber is taken, flows from these veins and down the center vein into a little cup which the natives place to receive it. After the little cups are filled they are gathered and brought into the rubber camp, and there the latex is coagulated by means of smoke. This is done by the use of a paddle which is alternately dipped into a bowl of the latex and then revolved in the smoke from a wood or palm-nut fire. This smoke seems to have a preservative effect on the rubber as well as drying it out and causing it to harden on the paddle, each successive layer of the latex causing the size of the rubber ball or biscuit to increase. When a biscuit of sufficient size has been thus coagulated it is removed from the paddle and is ready for shipment to countries where rubber products are manufactured.

Para rubber is sold in three grades. Fine Para, which is the more carefully coagulated or smoked rubber; Medium Para, which is rubber gathered and smoked in the same way as Fine, but which has had insufficient smoking, and, therefore, more subject to deterioration due to oxidation, etc.; and Coarse Para, which is rubber gathered from the drippings from the rubber trees after the cups have been removed. This latter grade has generally a large percentage of bark and other foreign substances mixed with it, and is subject to even more deterioration than is Medium Para, as it is oftentimes not smoked at all.

Another important grade of rubber coming from South America is Caucho. This tree grows similar to the Para trees and the rubber is gathered in a similar manner, but is cured by adding to the latex some alkaline solution and allowing the whole to dry out in the sun. The value of this rubber can be greatly improved by better methods of coagulation.

From Central America and Mexico comes the Castilloa rubber. This rubber is gathered from trees in a very similar manner to Para, and is coagulated by being mixed with juices which are obtained by grinding up a certain plant which grows in the Castilloa districts. After being mixed with this plant juice, the Castilloa is spread out in sheets on bull hides, where it is allowed to dry in the sun, after which the rubber is rolled up and is ready for shipment. Castilloa is gathered mostly from wild trees, but in Mexico it has recently been cultivated to some extent.

From Mexico we also get Guayule. This rubber is obtained from a certain species of shrub, the shrub being cut down and fed into a grinding or pebble mill where the branches are crushed and ground and mixed with water, and the rubber, which is contained in little particles all through the wood, is worked out, being taken from the pebble mills in chunks as large as a man’s fist.

From Central Africa and from Borneo come the so-called African gums, such as Congo, Soudan, Massai, Lapori, Manicoba, Pontianic, etc. Some of these rubbers are gathered from trees, but most of them from vines and roots, and the methods of coagulation are varied. Practically all of them are dried out in the sun. These rubbers are all of lower grade than the Para rubbers of South America.

The Story in a Stick of Chocolate

Where Does Chocolate Come From?

Perhaps no other one thing is so well known to boys and girls the world over as chocolate. Yet there was a time, and not so many years ago, as we figure time in history, when there were no cakes of chocolate, or chocolate candies to be had in the candy shops, no chocolate flavored soda water or chocolate cake. To-day quite a panic would be started if the world’s supply of chocolate were cut off.

Chocolate is obtained from cacao, which is the seed of the cacao tree. It is quite often called cocoa, although this is not quite a correct way of spelling the word. The cacao tree grows to a height of sixteen or eighteen feet when cultivated, but to a greater height when found growing wild. The cacao pod grows out from the trunk of the tree as shown in the picture, and is, when ripe, from seven to ten inches long and from three to five inches in diameter, giving it the form of an ellipse. When you cut one of these pods open, you find five compartments or cells, in each of which is a row of from five to ten seeds, which are imbedded in a soft pulp, which is pinkish in color. Each pod then contains from twenty-five to fifty seeds, which are what we call “cocoa beans.”

The cacao tree was discovered for us by Christopher Columbus, so that we have good reason to remember him aside from his great discovery of America. The discovery of either of these would be fame enough for any one man, and it would be difficult for some boys and girls to say just which of the two was Columbus’ greater discovery.

Columbus found the cacao tree flourishing both in a wild and in a cultivated state upon one of his voyages to Mexico. The Indians of Peru and Mexico were very fond of it in its native state. They did not know the joy of eating a chocolate cream, but they had discovered the qualities of the cacao bean as a food and had learned to cultivate it long before Columbus came to Mexico.

Columbus took some of the cacao beans back with him to Spain and to this day cacao is much more extensively used by the Spaniards than by any other nation. The first record of its introduction into England is found in an announcement in the Public Advertiser of June 16, 1657, to the effect that:

“In Bishopgate Street, in Queen’s Head Alley, at a Frenchman’s house, is an excellent West Indian drink called chocolate, to be sold where you may have it ready at any time and also unmade, at reasonable rates.”

Of course, by the time America became settled the people brought their taste for chocolates with them.

What is the Difference Between Cacao and Chocolate?

When the cacao seeds are roasted and separated from the husks which surround them, they are called cocoa-nibs. Cocoa consists of these nibs alone, whether they are ground or unground, dried and powdered, or of the crude paste dried in flakes.

Chocolate is made from the cocoa-nibs. These nibs are ground into an oily paste and mixed with sugar and vanilla, cinnamon, cloves, or other flavoring substances. Chocolate is only a product made from cocoa-nibs, but it is the most important product.

WHERE THE SHELLS ARE SEPARATED FROM THE BEAN.]