On 17/09/2010 18:31, Dave Osborne wrote:
John Rumm wrote:

Well, the Oxalic acid worked like magic.

Result!

There seems something slightly counter-intuitive about correcting the
effects of one acid by application of another.


Well, I haven't even begun to think about the chemistry. The tan colour
just faded away in a few minutes without any fuss or fizzing. As you
say, Result!

It was always recommended as a bleach for wood, though I never figured
out how it would work.