Bleach Can Erase Water Stains

House Doctor | Gary Dymski

September 28, 2000

Q. About 10 years ago, we renovated our home. We put in interlocking cedar panels on the walls and ceilings, but we had a problem with water damage. We have water stains in one area of the ceiling. How can we get rid of these?

We left the wood natural; we never applied any sealer, stain or protective coating on it. These water stains look awful.

-Rose Williams, Baldwin

A. Before you remove the water stains in your cedar planks, be sure to solve the bigger problem: the leaks in your ceiling or walls. Once you've patched the leaks, you can try bleaching the stains away.

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Wood bleaches can be found in paint stores and home centers. They typically come in three types: peroxide bleaches, chlorine bleaches and oxalic acid. Peroxide bleaches remove most natural color in wood, and chlorine bleaches remove or lighten most color stains. Oxalic acid removes "black stains" that are created when tannic acid in the wood comes into contact with moisture and iron, usually from nails. You sometimes see these types of stains in natural wood floors. Oxalic acid is the primary ingredient in the many products sold as deck brighteners.

Consult with a specialist at your favorite paint store, but an oxalic acid solution might be your best bet. The acid comes in crystals and must be mixed with warm water. Don't pour the water over crystals, but rather slowly add crystals to the water. Use a glass jar (32 ounces or more), and stir the crystals in gently. When no more crystals will dissolve in the water, you have a saturated solution. Wear rubber gloves and apply with a nylon brush. Let the wood dry. To remove the stain completely, you might have to apply the solution a second time. Rinse or swab the wood with distilled water.

Before working on a large area, I'd suggest applying in a small area to test the results.