Shellac is an animal product, a resin secreted from the Coccus lacca (lac beetle), a scale that feeds on certain trees in India and southern Asia.
After feeding, the insect secretes a resin, which dries and hardens into a protective covering called lac. The lac is collected, crushed, washed, and dried. After cleaning and heating, it is drawn into thin sheets of finished shellac.
The level of refinement, the timing of harvest, and source of the lac, determine the specification color
Shellac is a spirit-varnish resin. Often, oleo-resins are added to increase the elasticity. Sandarac, mastic, and Manilla copal are sometimes mixed with it, and dragon's blood or gamboge is occasionally put in for colouring.
Shellac varnish gives a smooth finish and a high polish. The film is tough but not completely water-resistant. it is used as a primer for wood because it prevents any resin escaping and affecting the paint film and because it is impervious to the solvents ordinarily used for fresh oil paint. In restoration, it is sometimes applied as a weak primer over filling gesso in the losses of a paint film, for it has the property of being wetted with water and so will take an aqueous medium. Its colour and slow solubility keep it from being much employed in connection with paint.
Dissolve the shellac flakes in ethanol, a combination of alcohols or Shellac Solvent. Often other natural are added (Sandarak, Mastic and Manila Kopal).
The usual percentage of dry shellac flakes in alcohol is 12-20%. Leave overnight and filter. Store the prepared shellac finish up to 6 months (the drying time prolonges with older polish).