Gordon inscribed in red ink for all to know:
I tried it yesterday. Heavy on the oxalic in hot water. Used paper towels
wetted down and left on the spots for an hour. Yup, black is still there!
Gordon
"Dave W" wrote in message
...

Somewhere, someplace there must be someone that has had good luck getting
rid of dark areas in poorly maintained brightwork using oxalic acid. It

has

never worked for me.....sometimes the black is a little lighter but not

much

better.
Dave
"RW Salnick" wrote in message
...

Gordon inscribed in red ink for all to know:

I have some old varnished wood I want to strip down and reuse. This
wood
has black areas around the old screw holes. How do I get rid of the

black

w/o sanding away all the wood?
Thanks
Gordon



oxalic acid should take care of them...

bob





Hi Gordon -

I assumed that the black stain was iron - either leached from iron/steel
fasteners, or from the action of iron-fixing bacteria. Oxalic acid is
quite specific for iron stains.

But black stains could come from other things too. Almost all metal
powders look black. Metal powder could come from continued action of a
fastener working in a hole, wearing away a fine dust of fastener and
embedding it in the wood (eg. check your rag after using brasso...). I
do not know how to remove this dust (and the method would depend on the
particular metal involved) without damaging the wood.

Also, the black could be due to bacteria colonizing the wood where it
was unprotected by varnish, and had access to moisture. In this case,
regular cholrine bleach will do a good job.

bob