This story covers stripping paint and varnish.
Some finishing projects will require only minimal preparation. Painted trim or furniture whose surface is in good condition may need only a good cleaning or some scraping and sanding. Items in rough condition, with multiple layers of paint poorly applied or some of which are coming off, will need stripping, no matter what kind of finish you're reapplying. This is especially true of wood trim and a necessity if you're changing from a latex to an oil-base finish, or vice versa, or restoring a painted antique to its original unpainted state.
Stripping solutions come in a variety of forms, from "cold" (with minimal health, fire, and environmental concerns) to "hot" (fast acting but posing potential health and environmental risks, therefore requiring careful precautions).
No matter what kind of stripper you use, wear heavy rubber gloves, eye goggles, old clothing, long-sleeve shirts, and a respirator. Do not use solvent-base strippers in a room with an open flame (a stove, water heater, or furnace pilot light, for example), and provide your work space with ample cross-ventilation.
Set up a receptacle for disposing of the finish you remove; an old paint can is a good choice, but several thick layers of newspaper will allow you to spread out the removed finish in a relatively thin layer so the stripper can quickly evaporate from the old finish. Once evaporated, you can safely dispose of the dried finish in plastic bags. Check with your trash removal agency to see whether the dried residue can be included in your regular trash pickup or if it must be taken to a special location.
If you use rags in any part of the stripping process, soak them in water and hang them outside to dry before disposing of them. Solvent-base strippers, especially, are prone to spontaneous combustion if wadded up in a closed container (like a trash bag) before the solvent has completely evaporated.
Using an old natural-bristle brush (some strippers will melt synthetic bristles), apply the stripper in a heavy coat, brushing in one direction only. Rebrushing stripper will only remove it before it can do its work. Apply stripper to an area only as large as you can remove before it dries.
Leave the stripper undisturbed on the surface until bubbles begin to appear. Then wait longer. Most modern formulations will remove multiple coats if you let them work long enough. Then scrape the varnish up with a putty knife, depositing it in a metal disposable can or on newspapers.
While the surface is still damp from the stripper residue, wash it several times with denatured alcohol. Use a pad of #0000 steel wool or a fine abrasive pad to clean the residual stripper from the surface. Be sure you get it all. Residues will interfere with your finish coatings.
Refinishing solutions are not made for paint removal, but they do remove varnishes and other clear finishes quickly.
To use a refinisher, pour a small amount of the solution into a pie tin or other small container. Soak a pad of #0000 steel wool in the refinisher and apply it to the surface, removing the finish with light circular scrubbing motions. Squeeze the dissolved varnish back into the refinisher and reapply until the finish is removed.