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Shellac:  What it is

 

Shellac refers to all forms of purified lac - a natural resin secreted by the tiny lac insect on certain trees, principally in India and Thailand.

Known for three thousand years, lac provided the natives of India with colors for clothing and a material they fashioned into ornaments and trinkets. It first became commercially important for the purple-red dye extracted from it to dye textiles. It was prized as a decorative lacquer as far back as the sixteenth century.

Aniline and other chemical dyes have long replaced lac-derived dyes. However, despite the many synthetic resins produced by the chemical industry, natural shellac still retains an important place in the decorating products field as well as in such diverse applications as pharmaceutical, candy and fruit coatings; printing inks; furniture finishing; adhesives; grinding wheels; hat stiffening; and paper and foil coatings.

How Insects Make Shellac
Shellac is produced by a tiny red insect (Lac Laccifer) which, in its larval stage, is about the size of an apple seed. Swarms of the lac insect feed on host trees, commonly called "lac trees."  Their life cycle, of about six months, is devoted to eating, propagating and making lac as a protective shell for their larvae.

During certain seasons of the year, lac insects swarm in such great numbers that the lac trees can take on a red or pinkish hue. When settled on the twigs and branches, they project a stinger-like proboscis to penetrate the bark. Sucking the sap, they begin absorbing it until they literally feed themselves to death. At the same time they propagate, each female producing about one thousand eggs before dying.

The sap the insect is consuming during this period undergoes a chemical transformation in its body and is eventually exuded. On contact with the air, it forms a hard shell-like covering over the entire swarm. In time, this covering becomes a composite crust for the twig and insects.

The female insect is the main shellac producer. While she is exuding lac, she is preparing herself to die after providing a fluid in which her eggs will mature and from which the future supply of bugs will come, to repeat the process of swarming, propagating and making the next season's shellac supply.

The males, having fertilized the hordes of females, also begin their life-ending feast. Although they contribute relatively little more to the shellac crop, they have already assured an ample supply because the females vastly increase their output of lac after being fertilized. The great mass of male and female bugs on each tree gradually becomes inactive as the shell-like covering forms over them. In the sixth or seventh month, the young begin to break through the crust and swarm to new feeding grounds.

Shellac cultivation is carried on to produce a large lac crop by helping the larvae find better pickings for their feast. This involves simply cutting lac-bearing twigs from an infected three a few days before the emergence of the larvae. A bundle of such twigs, known as 'broodlac,"is tied to an uninfected tree on which there are many tender new shoots. This results in a higher survival rate of insects and a greater yield of lac since only a little broodlac gives forth sufficient larvae to infect a tree thoroughly. No further attention is needed until shellac is harvested.

How Lac Is Harvested
Shortly after the young have swarmed at the end of the adults' life cycle, natives begin to harvest the lac encrustation from the trees. Only one crop is taken from a single tree. Young are hatched, however, twice a year.

Natives gather millions of encrusted twigs, called "sticklac," for transport to simple factories or refining centres where the encrustations are scraped off. They may also break the encrustations off right in the forest or orchard with a wooden mallet, much the way ice can be broken from around a tree branch. This material is called "grainlac." In either case, this is the first step in the harvest of shellac gum.

At refining centres, sticklac is scraped to remove the resin from the twigs and then it is ground (as is grainlac), usually in a primitive mill consisting of two millstones, with the upper one rotated by hand. At this stage, the ground lac contains a mixture of resin, insect remains (shells, excrement, body parts), twigs and other impurities. This is now passed through a coarse screen to remove the larger impurities, like twigs.

After the lac is ground and the chaff sifted out, it is soaked in water for several hours in large cup-shaped jars. These are about two and a half feet high and have rough serrated inner surfaces. Next a worker called a "ghasandar" jumps into the jar and rubs the lac with his feet against the rough surfaces. The object is to break open the lac seeds so the dye will flow out and the insect remains will be freed from the resin. Dye water and scum are removed in several rinsings. Then, the ground lac is spread out on a concrete floor to dry in the sun.

The semi-refined product from this operation is known as "seedlac" from its grain-like appearance. It is yellow to reddish-brown in color, depending on the type of tree and the location from which it came. This is the raw material from which both orange flake shellac and bleached shellac are made.

Bleached Shellac
Even though most of the bright red lac dye is removed when sticklac is washed, some shade of orange persists. When dissolved in alcohol, orange shellac forms an amber-colored solution and the dried film has a distinctive amber cast. For many uses, however, a colorless film is preferred. To meet this market preference, the color is removed by a bleaching process.

The process involves dissolving seedlac, which is alkali-soluble, in an aqueous solution of sodium carbonate. The solution is then centrifuged or passed through a fine screen to remove insoluble lac along with any dirt and other insoluble material. Next step is bleaching the solution with dilute sodium hypochlorite to the desired light color. The shellac is then precipitated from solution by the addition of dilute sulphuric acid, filtered off, washed with water, ground and dried in vacuum driers.

The final product is a while powder commonly referred to as bone dry shellac, which dissolves in alcohol to give a milky white solution. The opaqueness is caused by the natural wax content of shellac which settles out on standing, leaving a clear solution above. The wax is easily re-dispersed and should be stirred back into suspension before use. Solutions of bleached shellac have traditionally been called "white shellac" to distinguish them from orange shellac solutions. This is somewhat of a misnomer because they dry to a clear, colorless film.

CONCLUSION
Clearly, lac, and anything that is coated with lac/shellac is tame’.  Lac is called by many names in the food processing industry, some of which are:

  • Food Grade Wax
  • Confectioner's Glaze
  • Food Glaze
  • Resin

One should keep in mind that Rabbanites permit the consumption of lac.  Therefore, many foods which bear a "kosher" label may contain lac, and would therefore be tame’ (not kosher).