Good morning citygirl ........... I own a home, that I purchased a little over a year ago, that has oak flooring in all areas except two of the bedrooms. In one area of the dining room wall there is an irregular black stain about 1&1/2 ft. wide by 3 ft. long. I received estimates from two different companies that specialized in re-doing oak floors. Both said the only way to totally remove the black was to replace the boards. The sanding down process would most likely have to go so deep that this area would have a depression compared to the rest of the floor.
My solution, which did not totally get rid of the black stain, but did soften it considerably was as follows: First I hand sanded the surface finish off this area. I then taped off the area from the surrounding flooring. I made a paste using flour and household bleach. Mixture was about like pancake batter. Smoothed it on with a putty knife and covered it with an old damp towel. I did this on a "football Sunday" so I could keep dampening the towel every so often. I used a spray bottle of water for this. Seem like I left the paste in place around 6 hours.
The result was very good but not complete. The stain was definitely lighter but not gone entirely. I went through this whole process again a week later. This time no change at all.
If you use this method or similar with a liquid soaking into the wood, the surface will need to be re-sanded and re-finished. The grain of the oak will be raised from the liquid soaking on the bare wood. The re-finish wasn't much of a job since it was such a small area. Just use a closely matching stain, and then apply a finish sealer in whatever level of gloss matches the existing floor.
Thank you, XXXXX XXXXX question..... Dennis (cut2it)
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