How do I remove dark water stains from my cedar ceilings? Bleach? Sanding? Sandblasting? The roof leaked previously (will soon be fixed) and I'd like a method that is not back (or neck) breaking to fix various spots. Is this something only a professional should attempt? Thanks.
The only way to remove black water stains from wood is to sand it away. But unfortunately since the stain is on the ceiling the water stain most likely penetrates too deeply into the wood to remove through sanding. Although there are websites that say otherwise, bleaching will do little to nothing to remove the stain. What you can do to disguise it is to either stain the ceiling a darker color or veneer over the portion of the ceiling that was damaged. Another option may be to replace the damaged panels of the ceiling completely and staining the new wood to match.
I remove dark water stains from table tops by bleaching the wood with oxalic acid (wood bleach). It works every time. But a ceiling can be problematic as gravity is working against you. Try putting a mixture of hot water and oxalic acid in a spray bottle and spray your ceiling. Then work it in with a sponge. Once it dries completely, it will lighten the cedar and hopefully the water stain along with it.
Of course, you will have to strip it the finish off the ceiling if one has previously been applied. Once you've done this, palm sand the ceiling to knock down any raised spots (if any) and to smooth out the surface for refinishing.
found this in the Washington Post (via the Star Tribune in Mpls) Toolbox: water stains
Published December 10, 2003
REMOVING WATER STAINS
Are you wondering how to get water stains off tongue-and-grove wood ceilings after roof leaks?
First, repair the roof leak and permit the wood ceiling to dry completely. Then, go to a paint supply company for wood bleach, which generally is applied in two parts. The first solution is applied directly to the stained area and left for about five minutes. Then, while the surface