You have this fantastic-sounding baby grand piano, but the exterior looks so disreputable you can barely stand to look at it. Stripping the old finish and applying fresh stain can make the piano look great--and it may help the piano sound even better.
You don't want the action and strings to be subjected to the dust and vibrations that come with stripping, so the entire interior should be removed from the casing before stripping. While the parts are out, it is good time to rebuild the action, if necessary, and replace any worn strings. Once the workings have been taken out, it is time to refinish the soundboard.
The soundboard can be compared with the speakers in a stereo system and is often the part of the piano that needs the most work. Humidity can cause cracks that affect the sound of the instrument. Years ago, it was said that a cracked soundboard meant a ruined piano, but, with today's glues, the soundboard can be restored to the original sound it was intended to have. After the insides of the piano have been removed, remove all dust with a damp cloth and check for cracks. Fill any cracks with a two-part epoxy glue and allow to cure thoroughly according to the manufacturer's directions. When the glue has dried, sand the soundboard with 60-grit sandpaper and vacuum the dust. Repeat the sanding with 90-grit sandpaper and then with 120-grit sandpaper. Vacuum up all the dust and wipe the soundboard with a soft cloth dampened with mineral spirits. Apply at least two coats of clear polyurethane finish following the manufacturer's directions.
Before refinishing the cabinet and other exterior parts of the piano, you must decide which stripper to use. All three of these will do an effective job and will not cause damage to the piano.
Methylene chloride is an effective paint stripper. Due to health and environmental concerns, some communities have made it illegal to dispose of the waste through the sanitary sewer system. After applying methylene chloride to your piano, it should be allowed to work before scraping it away with a putty knife. After stripping, the surface needs to be sanded well to remove any remaining residue. If the piano refinishing is going to be done in the area the piano normally is set in, methylene chloride would probably not be a good choice of stripper because of fumes and environmental concerns.
Pianos built before the 1970s would not benefit from using aqueous paint strippers; they were not finished with polyurethanes or epoxies. With newer pianos that need refinishing, aqueous paint strippers would work well. Aqueous strippers work by breaking the bond of the paint to the surface. Since aqueous paint strippers are water-based, they tend to open the wood pores requiring more sanding than solvent type strippers. Some aqueous strippers contain sodium or potassium hydroxide, which generates heat to make the stripper more active. Aqueous strippers can be applied by painting the product onto the desired surface.
Solvent strippers work by dissolving or softening the paint so that it can just be wiped up with dry rags, making them ideal to use on pianos because they are relatively easy to use and would not necessarily require that the piano be removed from the area it is used in. Stubborn spots of paint that won't wipe up can be scraped away with a putty knife. Solvent strippers can be painted on, but should not be sprayed because the vapor contains hazardous air pollutants.
The Environmental Protection Agency does not consider strippers made from the terpenes of pine or citrus hazardous. Piano refinishing with biochemical strippers is effective, but does not work as quickly as other strippers, so repeat applications may be necessary, or applying stripper-soaked cloths to allow the stripper more time to work may also help biochemical strippers do their job.
Refinishing Without Stripping
If the surface of the piano is in relatively good condition, you may not have to strip the cabinet at all; in this case, you may be able to use the method of wet sanding using mineral spirits to rough up the surface. After sanding with 120-grit sandpaper and mineral spirits, the surface should be wiped down with soft, clean Turkish towels just barely damp with mineral spirits. There may be some white residue remaining, but it is all right to coat the piano with a fresh coat of polyurethane.
Restoration of Non-Wood Parts
Before reinstalling the metal parts, shine them with metal polish. If the screws need to be replaced, try to match the old screws. Polish the pedals and connecting rods and coat them with clear polyurethane. Replace any broken or missing piano key tops (see Resources).
If you just want to finish only the exterior of the piano; the action, keys and strings should still be removed to prevent them from being damaged. Protective eye wear and face masks should be worn when stripping with methylene chloride. Because of the caustic nature of aqueous strippers, protective clothing including vinyl or rubber gloves should be worn. Protective clothing, face masks and safety glasses should worn when using solvent strippers. Use tarps to protect the area under and around the piano.