On Wed, 19 Oct 2005 13:03:07 GMT, Stuart Noble
wrote:

If it's filthy, then Barkeeper's Friend will shift it. It's based on
oxalic acid and a good hardware shop, kitchen shop or even supermarket
will have it.

It seems to be the basis of decking cleaners (a new must-have for the
makeover brigade). Quite what it does, and how, isn't immediately clear.
I've never found it effective as a wood bleach.

As John said, it's particularly good on iron oxides. Its only real use
as a wood bleach is for removing metal stains, even blue iron stain on
oak.

It's good on hardwood decking, but can be a bit harsh on resinous
softwood (larch) decking. If you do use it on teak or brownwood kurtzii,
then it's important to re-oil the finish afterwards.