How to Remove Dark Stains From Furniture Stripping

Treat stains in a well-ventilated area.

When refinishing a piece of furniture, you're likely to encounter dark stains that may be from furniture stripping but are more likely caused by water stains, according to J.R. Reding Co. Antique Furniture Restoration. These stains have often permeated the surface of the wood and will mar any finished piece if not removed. Oxalic acid crystals, available at hardware stores or drugstores, act as a powerful wood bleach that will remove the dark stains and freshen the entire surface of the wood. Oxalic acid also removes a previously applied furniture stain.

Things You'll Need

• Extra-fine sandpaper
• Tack cloth
• 2 to 4 tbsp. oxalic acid
• 1 pt. hot water
• Plastic or glass bowls
• Wooden mixing spoons
• Paint brush
• Sponges
• Dry cloths
• 1 tbsp. clear ammonia
• 1 qt. hot water

Instructions

1. Sand the furniture lightly with sandpaper to remove any oils or grit from the furniture stripping process. Wipe the furniture with tack cloth to remove dust and debris.

2. Mix 2 to 4 tbsp. oxalic acid, depending on the severity of the stains, in 1 pt. hot water in a glass or plastic mixing bowl. Don rubber gloves and goggles and wear protective clothing.

3. Paint the entire wood surface with the oxalic acid mixture using a paint brush. Don't dip the metal strips on the paint brush in the mixture. Wait 10 to 20 minutes and re-apply if necessary.

4. Mix 1 tbsp. clear ammonia with 1 qt. of water. When the wood has lightened sufficiently, wipe the ammonia on the furniture with a sponge to neutralize the oxalic acid and halt the bleaching process.

5. Dip a clean sponge in water and wring it out. Wipe the entire surface thoroughly with the sponge to remove the bleach and ammonia.

6. Wait 24 to 48 hours until the furniture is completely dry. Sand the surface lightly to remove the gray coating left by the bleach. Oxalic acid may raise the wood grain. Sand out any raised grain before re-finishing the piece.

Tips & Warnings

• Open windows to provide ventilation when working with oxalic acid. Lay a tarp down to protect surfaces.

• Never mix oxalic acid in a metal container or use metal implements. Doing so can release toxic fumes.

• Sand in the direction of the wood grain.

References

• Utah State University Cooperative Extension: Removing Spots, Dents and Surface Imperfections
• J.R. Reding Co.: Bleaching Water Stains From Furniture

Resources

• Utah State University Cooperative Extension: Cleaning, Repairing and Reconditioning Wood Furniture