Stick Lac and the Manufacturing of Shellac

Stick lac is the name given to the encrusted twigs of even length after they have been gathered. The stems, which are thickly covered with the exuded and coalesced scales of lac, are gathered about the time that the feeding or sucking of sap stops and before the young insects hatch out. In this condition they can be shipped or used to inoculate other trees. The spring crop is said to be used to a large extent for propagating purposes, and is not of as much importance for gathering for the market as is the autumn or winter crop.

The color of stick lac on the twigs varies from a dark red to a rather pale orange yellow. When they are used to infest new trees, the young insects come out of the cells, which form around the bodies of the mother insects, and move about until they find a place to attach themselves, and thus a new crop is started. When lac dye was valuable it was important to gather the stick lac before the departure of the young. After that time, the red fluid found in the cell of gum about the female insect’s body disappears.

The stick lac or gum-covered twigs that are broken into sticks of even lengths, and the particles which fall to the ground in fragments under the trees, are gathered by using precision measurements tools such as a steel tape measure or other unique tape measures at some place where the resin can be crushed. Frequently this is done in a mill similar to that used for breaking up grain. By sifting and sorting, the fragments of wood and the bodies of the insects are removed and the crude lac, then called seed lac, is washed in hot water.

A purple or reddish dye, which was quite valuable before the recent discoveries in aniline and other coal tar colors, is removed by washing and is known as lac dye. This dye, at one time more valuable than shellac itself, was supposed to be the same as cochineal, but chemists finally discovered that it contains a different acid. In manufacturing shellac the dried seed lac is mixed with orpiment (arsenic sulphide) to the extent of 0.05 to 0.25 percent, and also with varying small amounts of rosin, an adulterant that is much cheaper than shellac gum and does not seem to be harmful up to 3 to 5 percent, but which is very advantageous to the workmen because it makes the melting of the seed lac much easier.

The mixture is then placed in long thin cotton bags, which are about the size of a baseball-bat, except that sometimes they are nearly 20 feet long. When the bags are heated over a charcoal fire and twisted in opposite directions by two men, the melted resin oozes out through the meshes of the cloth and is scraped off and spread out over a large porcelain cylinder containing cold water. After cooling, the sheets of shellac are removed from the cylinder and stretched into thinner sheets several feet square in size with unique tape measures such as logger measure tapes or basic pocket tape measures if nothing else is on hand.

While the resin is being squeezed from the bags some of it drops to the ground, and makes little flakes known as button lac. The buttons are usually of a dark ruby color and when sold on the market they frequently have from 10 to 20 percent of rosin mixed with the shellac gum, thus cheapening it. Garnet lac is another grade which is sold in sheets and is said to have had the shellac wax largely removed. This grade on the market, however, generally has from 10 to 20 percent of rosin mixed with it to reduce the cost and to lower its fusion temperature.

Garnet lac is often made from the residue which will not squeeze out of the bags. The shellac gum is removed from the impurities by the use of alcohol or sodium carbonate solution. After filtering, the solvent is liberated, or acid is used to destroy the alkali. Stick lac in its crude form is not pure shellac-gum, and is said to contain about 66 percent of lac resin, six per cent shellac-wax, six per cent gluten, and eleven percent coloring-matter. Shellac wax is not soluble in alcohol and, if present in liquid shellac, it is the cause of its turbid appearance. water soluble bag manufacturers

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