Bronze Effects.—An interesting point in connection with the use of the Basic dyes, and some of the Acid dyes, too, for staining leather is that, when applied in a strong solution, as is very likely to be the case when one is trying to get dark shades with an application of the brush or pad, they quite frequently, on drying, show a very marked metallic lustre. This is due to the formation of minute, bright-colored crystals, which reflect the light, thus imparting to the fabric colors which have nothing to do with the shade produced by the dyestuff itself. Thus, Cyanole FF, Cassella, when dissolved, or when dyed on leather or any other material, gives a rather greenish shade of blue. But it gives a very brilliant old gold effect, almost as bright as gold leaf, when applied in a strong solution and allowed to dry quickly.
When this effect is not desired it can be avoided by building up the dark shades by successive applications of weak solution, and by rubbing down the little crystals with, if necessary, a little moisture, whenever they appear to be forming.
In some cases, however, this bronzing property is of some value, and enables the skilful craftsman to obtain interesting and effective results with a minimum of trouble and expense. By painting on a strong solution of dyestuff, and letting it dry quickly, the bronze effect will be produced, and then by rubbing in portions, the true coloring of the dyestuff will be brought out in strong contrast to the crystal-covered surface. Unfortunately, these bronze effects are not fast to either rubbing or moisture, and even dry rubbing will break down the crystals, while rubbing with a damp cloth or a moist finger will dissolve the color off in blotches. To render this bronze effect more durable, it is possible to make a regular bronze lacquer, by adding varnish or gum like orange shellac or gum benzoin to a strong alcoholic solution of a Basic dye. The bronze varnish thus produced will, when dry, stand light finishing with wax in the usual way. The addition of a little benzoic acid to the solution increases the lustre of the crystals.
Chapter XI
SILK—I
So far as we can tell, silk was first discovered and manufactured in China about 1700 B.C., a date corresponding in Biblical history to the time of the patriarch Joseph. From China it was exported to the great and wealthy empire of Persia, and from there was first brought into Europe by Alexander the Great after his defeat of the Persian king. Its origin, although known and described by Aristotle, was for several hundred years a mystery. During the Roman Empire, silken garments, woven in Europe, from Chinese silk imported by way of Persia, were important and very highly prized articles of luxury.
About 555 A.D., while commerce with Persia was interrupted by warfare, two monks in the pay of the Emperor Justinian smuggled eggs of the silkworm and seeds of mulberry trees from China to Constantinople. This was the origin of the European silk industry. It spread rapidly to the various countries bordering on the Mediterranean, and by the seventeenth century was firmly established not only in Spain and Italy, but also in France.
Efforts were made to introduce it, at this time, into England, but without success. In 1622 King James I started the industry, for the first time, in the colony of Virginia in this country. Since that time numerous attempts have been made to develop the American silkworm industry, but with very little success, owing to the large amount of hand labor necessary to produce the material.
At the present time the very finest raw silk in the world is produced in the south of France, and next to that come certain brands of Italian silk. The Japanese silk is more variable in quality, although steadily improving, while the Chinese silk, as a rule, is less satisfactory and more apt to be light and fluffy.
With regard to the consumption, it was estimated that in 1907 Europe used some twenty-five million pounds, and the United States fifteen million pounds of raw silk, which, at an average price of nearly $5.50 per pound, amounted to over two hundred and eighteen million dollars.
Origin and Varieties of Silk.—Silk has been defined as a “smooth, lustrous, elastic fibre of small diameter and of animal origin.” As is well known, ordinary commercial silk is secreted or “spun” by the silkworm, the caterpillar form of a moth known asBombyx Mori, the moth of the mulberry tree. These silkworms have been cultivated for thousands of years, but there exist in different parts of the world, notably in India and Japan, wild or uncultivated silkworms, derived from nearly related, but not identical, families of moths, and whose silk is collected in the forests by the natives, forming what is known in commerce as wild or tussah silk.