Shellac is a natural product produced by the lacquer scale insect. It absorbs plant sap from trees and secretes a resin with which it protects its laid eggs. After the young aphids hatch, the encrusted resin left behind is harvested. The cleaned and dried resin is often dissolved in alcohol - as in the case of Clou Streich Shellac - to make it brushable.
You can use shellac to create transparent coats on old wood or to touch up. Shellac is only suitable for interior use, however, because it swells on contact with water. Shellac is not water-soluble, however, so surfaces painted with shellac can be wiped off with a damp (not wet) cloth. Shellac is often used to restore old musical instruments or furniture, since shellac existed as a precursor to plastic-based resins and varnishes. It thus often represents the original material used to coat interior woods over a hundred years ago.
The shellac surface becomes shinier with each coat applied. With a lot of effort, shellac can be used to create very impressive surfaces. To do this, the wood must be sanded well before the first coat, and intermediate sanding with very fine grit (320) is also important after each coat and fourteen-hour waiting period. Elementary, as with all varnish work, is the cleanliness and especially the absence of dust on the surface before varnishing.
Shellac is physiologically harmless, complies with EN 71-3 (safety of toys) and is approved for contact with food. In the food industry, shellac is used, for example, as E 904 for coating chocolate dragees or citrus fruits (not vegan, not vegetarian). However, carnauba wax is now often used instead of shellac so that the chocolate dragee melts in the mouth rather than in the hand.