Staining Windows
Sand or strip the existing finish. If the window is in reasonably good condition, sand it to smooth the finish and dull the sheen. Cover your work surface with an inexpensive drop cloth. Begin with a 120-grit sandpaper; once it is done most of the work, sand with a 180-grit sandpaper for a smoother surface. If the finish is badly damaged or unattractively made, then just remove it. On many newer windows the sashes pop out. To remove sashes on older windows, you may have to carefully pry off trim pieces. Brush paint and varnish remover onto the window sashes following the manufacturer's direction. Scrape off the finish with a putty knife. Rinse with the solvent recommended for the remover.
Fill holes; Use wood putty to fill flaws. Spot sand these areas when the putty dries. Go over the window with a tack cloth or damp paper towel. Unfortunately, no putty matches the wood exactly. If you stain the wood, a stainable putty absorbs the stain and comes close to a match, but it will not be perfect. Experiment with different brands to see which works best. If you are not going to stain, make your own putty. Get a few pinches of fine sawdust from the type of wood you will be patching, mix with five minute epoxy, and fill in any holes. After the epoxy dries, trim off any bumps with a utility knife or sharp chisel and then sand down. Get a smooth finish by finally sanding with 000 steel wool.
Mask panes. Use masking tape to avoid getting finish on the glass. The new, low tack tapes are easy to take off and leave less residue. They will work well when you mask off trim too. Use white or blue rolls instead of brown, they stick better. There are several types of low tack tapes so read the labels carefully, then choose the one that best fits your needs. Make sure you mask the two side edges of the sash. They are traditionally left unfinished so that the finish will not stick when you open the window.
Apply the stain and finish. If you have stripped the window and want to darken or warm it's color, stain it now. The stain will take evenly only if you've been thorough in removing the old finish. If the window is made of soft wood, such as pine, you will have an additional problem staining it. Soft wood absorb the stain unevenly, giving it a blotchy look. Avoid this by applying a gel stain, which will not blotch because it does not soak deeply into the wood. Apply at least 2 finish coats form greater durability; sills take the greatest beating and benefits from 3 coats. Sand lightly between coats, wiping up the dust with either a tack cloth or a damp paper towel.
Remove the masking tape. Remove the tape from the glass as soon as the finish begins to dry to prevent adhesive residue. If you have not taped off the glass, draw a sharp utility knife along the edges of each pane, leaving a narrow margin of finish on the glass. Push a window scraper toward this cut line to remove the finish.
