Chemical strippers--the preferred method of removing the finish from wood--fall into three categories, each with its own distinct properties and application techniques. All strippers contain caustic chemicals, so follow the manufacturer's recommendations to the letter, and wear heavy-duty rubber gloves and a respirator when using them. Work outside or in a well-ventilated room.
The most commonly used chemical strippers are those containing methylene chloride. These are available as a thick semipaste, designed to cling to vertical surfaces, and in liquid form, which is useful when stripping a piece with carvings or ornamentation. Both contain a wax component that slows evaporation, allowing the chemicals to remain on the wood longer.
Shake the can thoroughly to mix the contents before opening, then pour stripper into a shallow pan. Work on one small section of the piece at a time rather than attempt to strip the entire piece in one step.
To strip old paint, apply a thick coat of remover uniformly over the surface of a section with an inexpensive paintbrush. Leave the coating undisturbed for about 20 minutes, until the paint begins to bubble up. Remove the softened paint with a plastic scraper (Image 1). If necessary, apply a second coat of stripper.
After another 20 minutes, use a pad of coarse steel wool dipped in mineral spirits or lacquer thinner to scrub off the last bits of remaining paint (Image 2). Finish by wiping off the section with a soft cloth dipped in clean mineral spirits.
Note: The final step of rinsing the surface with mineral spirits or lacquer thinner is critical to avoid problems when sanding and staining. Avoid strippers advertised as "water-rinse" or "no rinse."
Methylene-chloride strippers are not the only option for removing old varnishes. Furniture refinishers--wax-free solutions containing a blend of solvents such as lacquer thinner, denatured alcohol and mineral spirits--are a good choice for removing varnishes such as shellac and lacquer. To determine whether a particular finish can be dissolved with furniture refinisher, perform this test: Moisten a cotton ball with a small amount of solvent-based fingernail-polish remover, and rub it on a small area of the finish. If the cotton ball turns brown, the finish is dissolving--indicating that it can be removed with a furniture refinisher.
Furniture refinishers contain no wax and evaporate quickly, so it's best to work on small sections at a time.
Pour furniture refinisher into a shallow pan, and dip in a soft cloth. Rub the moistened cloth over the old finish until it begins to dissolve. Rinse the cloth in the refinisher and continue rubbing. If the finish is particularly difficult to remove, switch to a pad of fine or medium steel wool dipped in refinisher. Finally, wipe down the surface with a soft cloth dipped in clean refinisher.
A third category of removers, known as "safe strippers," may be useful for those who are sensitive to harsh chemicals. Safe strippers contain fewer caustic ingredients, but they're generally more expensive and take longer to soften the finish. The techniques for using safe strippers are similar to those described above:
Shake the container of remover thoroughly. Brush a heavy coat of safe stripper onto a section of the piece, taking care not to over-brush (Image 1). Lay a piece of waxed paper over the remover to slow down evaporation (Image 2). Once the finish has softened, use a plastic scraper to remove it. Apply a second coat and cover with waxed paper. After a few minutes, scrub off the remaining softened finish with a pad of fine steel wool. Wipe the piece clean with a soft cloth.