Old furniture may have a shellac finish, probably refinished at home. Knotty pine rooms also were normally treated with shellac. Keep moisture away from shellac surfaces. Water or a damp environment, as in humidity, makes shellac sticky. Test in an inconspicuous spot with denatured alcohol; shellac will dissolve quickly. Vacuum or dust regularly with a soft, dry cloth; do not use oiled or treated cloth.
You may protect the finish with a liquid furniture wax or cream polish that gives the desired gloss. If dirty, clean with either a cleaning polishing wax for furniture. Follow the directions on the label for cleaning, or use a solution of equal parts of boiled linseed oil and mineral spirits. Moisten a soft cloth with cleaner and rub briskly, changing cloth when soiled. If surface is very dirty, process may have to be repeated. Use 3/0 or 4/0 steel wool to remove stubborn soil and smooth roughened places. If finish is in poor condition, use denatured alcohol to remove, and refinish with modern finish.
Test for Existing Finish on Furniture
Rub a Few Drops of Boiled Linseed Oil Into the Wood - If it absorbs, the wood has an oil finish. If it beads up, the wood has a hard finish (continue).
Rub Acetone Over a Spot in a Gentle, Circular Motion - Polyurethane finishes shed acetone like water. Lacquer dissolves in 30 seconds with rubbing. Varnishes and shellacs turn to a sticky, gel-like substance after a minute or two (continue).
Try a Few Drops of Denatured Alcohol - Shellac dissolves quickly in denatured alcohol. Varnish reacts slowly.
This article has been contributed in part by Michigan State University Extension