Furniture can develop water stains and mildew from a variety of sources. On the modest side, the furnishing might have been exposed to an unattended leak for a few days, while on the extreme end the furnishing might have been submerged for days in the course of a flood. Some stains and mildew problems are minor and can be cleaned off, but severe issues can only be cleared up with a full refinishing job.
Mix a batch of a mildew cleanser in a pail, using a cleansing agent like borax, trisodium phosphate or washing soda. Use 4 to 6 tablespoons per gallon or water, or as directed by the instructions. If your furniture is obviously too stained for cleaning, skip to Step 3.
Scrub the wood with the cleansing agent. Rinse with clean water. Allow the furnishing to dry and assess whether it is still stained and requires refinishing. If not, stop here. If refinishing is required, proceed to Step 3.
Sand off the old finish with a vibrating hand sander, an oscillating tool and hand sandpaper. Use the hand sander for the bulk of the sanding, the oscillating tool for corners and the hand sandpaper for fine detailing. Start with 60-grit sandpaper to remove the old finish and infected wood, then smooth out the rough sanding with 120-grit sandpaper, and conclude with 240-grit sandpaper.
Dust off the furnishing with a tack cloth.
Apply a suitable finish, such as lacquer, oil finish or wood stain, to the furnishing. Brush on the finish with long, even strokes and wait for that coat to cure/dry before applying a second. Some finishes, such as lacquer and oils, demand multiple coats.
Coat the furnishing with polyurethane, if appropriate. Stained wood furniture needs a coat of sealant, but lacquered furniture does not. Use the same long, even brush strokes and wait several hours between coats of polyurethane.
Tips & Warnings
- Preserving fine detailing requires that you do not remove too much wood while sanding, but eliminating ingrained mildew demands sanding off the infected surface wood. Ordinarily you should use only fine-grit sandpaper on detailing in order to preserve it, but the necessity of getting rid of the mildew may compel you to use coarse-grit sandpaper instead. Exercise particular care when hand sanding furniture trim and detailing, and do your best to preserve it.
- Some types of wood, such as oak, have an open grain that requires the application of grain filler before finishing.
- Always wear safety goggles and a dust mask whenever you employ power sanding tools, especially when the resulting sawdust might be packed with mildew.
Things You'll Need:
- Mildew cleansing agent, such as borax, trisodium phosphate or washing soda
- Scrub brush
- Vibrating hand sander
- Coarse-, medium- and fine-grit sandpaper
- Oscillating tool with wood sandpaper accessory pack
- Wood finishing product, such as lacquer or wood stain
- Paint brush
- Polyurethane (optional)
- Safety goggles
- Dust mask
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