Routine dusting and polishing will keep wood bright and the grain beautiful, but over time, dust, wax or polish can build up, especially in carvings, indented panels and embossing. Regular cleaning with a water- or solvent-based wash will soften old wax and remove grime. Wood with deeper stains may need abrasives to get it clean. The aim is remove the surface layer of grime and wax without damaging the natural wood's underlying patina
Anne Field, Michigan State University Extension Specialist, Emeritus, says the best way to clean old wood is with a vacuum or soft cloth. A cloth moistened with a solvent-based cleaning wax will pick up even more dirt. Dry the wood immediately with a clean cloth or soft paper towel.
For old furniture, cabinets and panelling with an undamaged shellac, lacquer or varnish finish, mix a little dishwasher liquid in water and wash thoroughly. Since unfinished wood will swell in water, use an oil-based cleaner like Murphy's Oil Soap. Apply generously and repeat until the wood is clean. Buff it with a soft cloth to restore its lustre.
Carol Williams, Extension Agent at Utah State University, says a mix of 3 tbsp boiled linseed oil and 2 tbsp turpentine in a quart of hot water is best for deep dirt. Turpentine will clean soil and oil and soften built-up wax and polish; linseed oil will replace the oils and restore bare spots. For a stronger cleaner, dip a soft cloth in white spirit (paint thinner) to rub away deposits of oil, greasy grime and old wax or polish. Always wipe wood dry and buff with a soft cloth after cleaning.
Wax, soil and oil build-up may require an abrasive to clean completely. While the best furniture finishes are usually thick enough to allow you to scrub white moisture rings away, dark rings mean the stain has penetrated to the wood and requires deeper cleaning. Abrasives include pumice and whiting power as well as toothpaste. They are used with ultra fine 0000 steel wool dipped in motor or linseed oil to scrub away stains.
Field recommends a regular deep cleaning with paste (carnauba) wax as the best protective wood cleaner. Rub a light coat on a small surface, wipe off the loosened dirt, then buff with a soft cloth until the wax is hard. Paste wax fills cracks in old wood finishes and prevents dirt from accumulating.
Cut old T-shirts into 8-inch squares for applying cleaners and buffing old wood. Soft toothbrushes dig grime from detailed areas and paintbrushes can deliver cleaner to narrow spaces. String will remove dirt from spindles and cotton swabs will clean curlicues in woodwork. Use toothpicks to get grit out of fine woodwork.