Oxalic acid

[kmealy]

On a furniture restoration forum, I frequently see people using oxalic acid as a "bleach."   I see two problems

 

1. They often opt for "Barkeeper's Friend", a scouring powder used to clean sinks and such.  While it contains oxalic acid, it's only 5% OA.  Savogran wood bleach is 95-100% oxalic acid.

 

2. While oxalic acid is one type of bleach, it's not a universal solution.  The most common use is for removing black stains caused by a reaction of tannins in the wood and iron, usually exascerbated by moisture.  It can also be used for graying due to exterior exposure. This article talks about three main types of wood bleach
http://www.antiquerestorers.com/Articles/jeff/using_wood_bleach.htm
 

 

If you do use oxalic acid, be sure to use PPE during application and rinse when you are done as if it dries in the wood and you sand the wood it can become hazardous.