SHELLAC

  
Seedlac is converted into Shellac either by traditional hand made process or comparatively modern machine made process.

HANDMADE SHELLAC……

Seedlac is converted into Shellac either by traditional hand made process or comparatively modern machine made process. Hand made shellac is produced by properly blending Seedlac into long narrow cloth bag and heating one end over charcoal fire and the other end is attached to a windless and is gradually twisted. The heat produced by the charcoal fire melts the lac which is forced out through the cloth by pressure. The molten lac is scraped out and drawn into sheets manually and left to dry. This process requires considerable manual skill and long experience. The traditional hand made grades are Lemon No.1, Lemon No.2, Standard One, TN Superfine etc. Hand made shellac is mostly exported to U.S.A., Germany, Japan etc. The impurity varies from 0.75% to 1.5%. 

MACHINE MADE SHELLAC…….

Is produced in two different ways- one is the heat process where the same principle as in the case of hand made shellac is applied and the second is solvent process where pure shellac is extracted from Seedlac by suitable solvents. Under heat process the separation of pure lac is achieved by melting Seedlac by steam heat and squeezing the soft molten lac through filter my means of hydraulic presses. The molten lac is then stretched by means of rollers into long continuous sheet which is broken into pleces to form the machine made Shellac under heat process. This shellac has an impurity content varying from 0.5 to about 1%. There are various grades under heat process machine made shellac. The most popular being TN, Lemon and Orange. These grades are exported to practically all lac consuming countries.

DEWAXED SHELLAC…….

Under solvent process wax and impurities are practically Completely removed by dissolving the seedlac in a suitable solvent, usually, chilled industrial alcohol. The solution is then filtered through fine cloth and the alcohol is recovered by boiling the solution. The molten shellac is then stretched to the required thickness on a roller. The product does obtained is known as Dewaxed Shellac. The most popular grades being Dewaxed Orange, Dewaxed Lemon, Dewaxed Garnet etc. Highly sophisticated grades of dewaxed and Decolourised Shellac can be produced by this method by adding activated carbon as the decolouring agent. The impurity is around 0.2%. Dewaxed or Decolourised Shellac are imported mostly by the advanced countries like U.S.A., Germany, U.K., Italy, France etc. 

USES OF SHELLAC

Due to versatility of lac resin, it finds innumerable uses both in industries fields. On the stand point of industrial uses of shellac one or more of the following properties are of great importance :

• Shellac dissolves in a wide variety of alkaline or rapidly drying alcoholic solvents but is resistant to a number of other solvents particularly hydrocarbons.

• Its film shows excellent adhesion to a wide variety of surfaces, possessing high gloss, hardness and strength.

• Shellac is powerful bonding material with low thermal conductivity and a small coefficient of expansion. Its thermal plasticity and capacity of absorbing large amounts of filters are noteworthy.

• Its electrical properties include high dielectric strength, low dielectric constant and characteristic freedom from tracking.

• It is resistant to the action of ultraviolet rays.

• Shellac is non-toxic.

Some of the main uses of shellac in different fields are :

• Surface coating – As under coat, primer, sealer French, Polish, Leather dressing, Fruit Coating etc.

• Printing – Flexographic ink, Waterproof ink, Photo engraving.

• Textiles – Stiffening of hats.

• Cosmetic & Pharmaceuticals – Hair lacquer, coating for Enteric pills, Dental base place.

• Engineering – Grinding wheels, Rivet & Plaste sealer.

• Electrical – Micanite, Insulating Varnish.

• Photography – Dry mounting tissue paper, protective varnish.

• Paper – Paper varnish, playing cards.

• Rubber – Stiffening agent, surface finish.

• Adhesive – gasket cement,sealing wax, pyrotechnic Optical Cement.