Stripping Paint and Varnish

Chemical paint removers come in many formulations, each with different strengths, benefits, and hazards. Some, like refinishers, have the thin consistency of solvents and are made for quick removal of varnishes and clear finishes but not paint. Others are enhanced with waxes and varying proportions of thickeners that slow their evaporation and help them cling to vertical surfaces.

-- Methylene-chloride strippers have one advantage that other solvent strippers do not -- they are nonflammable. When added to other solvent strippers, methylene-chloride makes them nonflammable also. This chemical, however, is harmful when inhaled and must be used with ample ventilation.
Methylene-chloride strippers work from the bottom up; they seep through the paint and remove it from the wood. The result is that the paint comes up in sheets, meaning you'll tend to use less of this product than others.
-- Solvent strippers work from the top down; they dissolve the finish layer by layer until they reach the wood. The paint you remove comes off as goo, not in layers. Although these strippers work more slowly, they don't evaporate as quickly as other strippers and don't raise the grain as much as water-base strippers. Pure solvent strippers are flammable, but many solvent products will contain a small amount of methylene-chloride to make them nonflammable.
-- Caustic strippers contain strong alkaline solutions, such as lye, and literally "eat" the finish off the wood. This is the only kind of stripper that will remove milk paint. Caustic strippers form a rubbery coating on the surface. When you're ready to remove the paint, most of it will come up in a single sheet. These strippers are less messy and can remove many layers of paint.

Caustic strippers are water-base, so they won't catch fire, but they are very harmful to skin and mucous membranes. These serious chemicals require appropriate protection, including good ventilation. In addition, caustic strippers will eat into the wood fibers and darken the wood if left on too long, so they require careful monitoring.

The least aggressive and easiest stripping solution to work with is a water-and-citrus-base product that is nontoxic, releases little odor, and is environmentally friendly. It works well but it takes a lot more time -- often as much as 24 hours -- to be effective. It can also raise the grain of the wood, which might require additional sanding.

Even though new products make stripping faster, easier, and safer, be sure to wear safety goggles, latex gloves, long sleeves, and a dust mask or respirator. Check for lead paint before beginning work.