Shellac is made from stik-lac which is deposited on branches of trees in India by sap feeding insects. It makes a good isolating sealer because it forms a very thin highly effective moisture barrier [two coats of shellac will reduce moisture absorption by 31%] without filling any grain, thus allowing subsequent paint or adhesive coats to grip the original substrate. Most widely used to isolate hydroscopic fireproofing chemicals before applying glue or paint. It can also be used as a floor polish and a fabric stiffener. Shellac dries in minutes.