Remove the existing finish on a banister by stripping it off, either by sanding or with a chemical stripper. The more thorough you are during the stripping process, the better your new application of stain will work and look. Start sanding with a medium-grit sandpaper to remove light nicks and dents, and the existing finish. If the banister is round, wrap a piece of sandpaper around the banister so that it covers as much of the banister’s surface as possible. With the sandpaper wrapped around it, move the sandpaper back and forth as you move along the entire length. Banisters with flat surfaces can be sanded with a sanding block. Sand the finish until the wood is bare. Sand the entire surface again with a medium/fine-grit sandpaper and then lightly once more with a fine-grit sandpaper. Ask an expert at your local True Value hardware store which exact sandpaper grit is best for your banister’s wood. If you don’t know the type of wood, it’s best to err on the side of caution and start off with as fine-grit sandpaper as you can use so you don’t damage it. Test it in an inconspicuous area on the banister.
If your banister is already installed, open windows or doors in the area. Otherwise, work in a well-ventilated area such as your open garage or on an outdoor deck or patio. Make sure your work area is dry and dust-free. When you begin refinishing, place a tarp or drop cloth underneath and secure it with masking tape where necessary. Use painter’s tape on any other surfaces you want to protect from drips and splattering.
If the banister is large, consider using a power sander. Take care not to damage the piece by sanding too deeply. Use medium- and low-grit sandpaper appropriate for the wood. Sand carefully by hand around decoratively curved areas.
For a new, bare-wood banister, simply sand it with fine-grit sandpaper before you stain. Remember to remove sanding dust with a cloth or clean rag.
Using chemical strippers is an easier method. Most chemical strippers need to be mixed with water, so check the manufacturer's directions before applying. Using a medium-sized paintbrush or clean rag, apply the solution evenly over the surface. Let it soak in for 20 to 30 minutes then use a plastic paint scraper, rag or sponge to wipe off the old stain. Once you've removed the old finish from the surface, use a clean rag to wipe it down so that the wood is completely bare. Let it dry.
If you use a chemical stripper to remove the old finish, it's a good idea to lightly sand the surface afterwards with a fine-grit sandpaper. This will ensure a tighter bond between the wood and the new coats of stain.
Always follow manufacturer's instructions and wear rubber gloves and protective goggles when using strong chemicals.
Never strip furniture near an open flame as stripping chemicals can ignite.
Use chemical strippers clearly marked "no cleanup" or "will wash away with water." However, the "no cleanup" type stripper may leave a residue, which must be sanded away. Residue from the "wash away" type can be removed by rinsing with water. Be aware that water may raise the grain of the wood. Lightly sand to reduce this effect. Heat guns can be used as a supplement to other methods to remove particularly stubborn finishes.