Restoration Workshop: Wood bleach
What you need to know about wood bleach
Chlorine bleach removes (or lightens) most dye stains without affecting the natural colour of the wood. It is readily available in a weak state in laundry bleach, and in the powdered form used in swimming pools. The powder intended for swimming pools is stronger and will likely require fewer applications. Mix the powder with hot water in a glass or plastic container until no more powder will dissolve’what you want is a saturated solution. Apply a liberal coat. Wait ten to twelve hours to see the full effects of the bleaching. Apply more if necessary. When the wood is the colour you want, rinse the wood several times with water. Chlorine tends to work well with dye stains but has little or no effect on pigment stains. (Pigments are large opaque particles that stay on the surface, dyes are much smaller particles that soak into the wood.)
Of course, most surface discoloration can be sanded out. But there’s a limit to the amount of sanding you can do on veneer, and sanding can’t change oak to maple. There may be a time when bleaching is the only available solution.
I read about a guy who was refinishing a little round table. The top was veneered in matching mirror-image quarters. One of the quarters had been stained with a bit of spilled india ink. Instead of trying to remove it, he carefully drew in matching mirror image india ink splotches on the other quarters. When he was finished, it looked like natural colour variation in the veneer. I have also watched a talented refinisher carefully change a small stain into a knot using an artist’s brush and some dark brown stain. It was a pine coffee table. When he was finished, the ‘knot’ was totally unnoticeable.