We have several large (3' x 6') blackened areas on our hardwood floor where water damage occurred. This discoloration goes deep. Our goal is to sand the floors and apply a clear coat, but we first want to know if there is a product that will remove the black stain. Also, if this cannot be done will a dark stain hide the problem?

  • Wood bleach, AKA oxalic acid, follow all directions on the product exactly.
    – Gunner
    Aug 25 '12 at 18:38
  • Thanks. Will this product penetrate into the wood as far as the black stain goes, or just bleach the surface?
    – RET
    Aug 26 '12 at 5:15
  • Does it matter? All you see is the surface.
    – Dave
    Nov 18 '15 at 20:38

Removing Dark Stains With Sandpaper

  1. Remove the finish over the stain gently with sandpaper, moving with the grain of the wood. Use #100-grit sandpaper, and then feather the edges with #150-grit sandpaper.
  2. Sand the stain with #150-grit sandpaper, now that you have removed the finish. Feather the edges around the stained area with #0000 steel wool.

  3. Use tack cloth (lint-free cloth) to remove sanding dust.

  4. Put on several light coats of varnish to match the original finish.

  5. Feather the edges of the new varnish with #0000 steel wool to remove the slight bump between the old and new varnish.

  6. Wax the wood with a quality polish.

Remove Dark Stains With Bleach

  1. Bleach the wood with chlorine bleach if the stain turns out to be too deep to remove without excessive sanding.

  2. Don your rubber gloves and apply the bleach with a brush.

  3. Let it sit for a few hours. The stain should fade to nearly the wood’s original color, but it’s a slow process.

  4. Use a clean sponge and water to remove the bleach completely and prevent further fading of the wood color.

  5. Apply vinegar to neutralize the wood. This will prevent the wood from lightening the stain or varnish when you brush it on.

  6. Let the wood dry thoroughly.

  7. Apply wood stain, if needed, and let it dry again.

  8. Brush on several light coats of varnish to match the original finish.

  9. Feather the edges of the new varnish with #0000 steel wool to remove the slight bump between the old and new varnish. Remove dust with a tack cloth.

  10. Wax the wood with a quality polish.

Taken from: http://www.wikihow.com/Get-Water-Stains-Off-Wood

  • -1: Links to other sites don't make good answers because they can go bad. Make sure the answer is here with links for additional information.
    – BMitch
    Sep 11 '12 at 10:47
  • Thanks for the advise! I'm just starting out as you can tell.
    – d4v3y0rk
    Sep 11 '12 at 11:13
  • We've all got to start somewhere. Welcome to the site Dave. I've removed my -1.
    – BMitch
    Sep 11 '12 at 12:10

The active agent in bleach is sodium hypochlorite. Normally, it will remove old stain color from wood but not ink stains or black water marks. For black water stains, use a saturated solution of oxyalic acid and hot water, then wipe with clean water.

The comment above which says to match the existing wood color with varnish etc., after stain removal, fails to mention that matching existing color can be extremely difficult. It's usually easier to refinish an entire top than to touch up a damaged one i.e., the long way is actually the short way.

Sand paper is usually a bad idea because it removes the surface of the wood, which is usually a different color than the wood immediately under the surface. Also very easy to sand through the veneer. Steel wool is a better way to go

  • The problem was solved in late 2012.
    – RET
    Dec 4 '16 at 16:06

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