Bleaching Water Stains Out of Oak

A refinisher succeeds in restoring oak cabinets using a hot, saturated solution of oxalic acid. August 14, 2007

I am refinishing an oak kitchen and the client wants it back to its original state. It has water damage that has caused the grain to go black. I stripped and scrubbed with a bristle brush, but still can't remove it 100%. The client wants no color whatsoever. Any tips on cleaning oak?

Forum Responses
(Finishing Forum)
Form contributor C:
In my opinion, you are trying to do the impossible. Oxalic acid will help lighten (bleach) iron stains (the most common that will blacken oak or other dark woods), but it is extremely difficult to remove all of the darkening unless it was very minimal to begin with. I have painted over such stains but this is a highly skilled art and still less than perfect. I'd be quick to let my client know that you can only fill his high expectations with brand new cabinets at the normal prices for that quality level and labor to remove the old ones and install the new ones.

From contributor D:
The black is caused by mineral stains. Make up a hot saturate solution (enough crystals until no more crystals will dissolve in the distilled water) of oxalic acid in a glass jar so that you can reheat it in a microwave and apply to the stained areas. You can repeat every 15 minutes or so 3-5 times, make a final application over the entire door/drawer, then let dry overnight. Next day rinse very well with distilled water until all of the crystals are absolutely gone. Leave the bristle brush alone - rips the soft wood out on oak especially. When dry, sand and proceed as expected. You may have to do some minimal touchup low down in the grain, but I'm betting you can do this.

From contributor R:
I'm steering towards contributor D's response. I have used oxalic acid with great results. Use it hot and do your bleaching in the direct sunlight if you can. Multiple steps will do wonders. Once the solution is completely dry and you have dissolved the crystal with hot water, make sure to wear a good particle mask when sanding the dried wood, because it will cause the most nose cleaning sneezes you can imagine.

From the original questioner:
Well, the cabs turned out great. I jut sprayed them today. The only problem I had was with the toe kick. It was 1/4" veneered waferboard, like the kind you find at Home Depot. I told her that I will change those parts for her. Other than that, I still find the kitchen looks ugly with no color, but then again I am not a big fan of natural oak on a kitchen.