Is this wood oak, by any chance? If so, the discoloration may not be due
to fungus/mold/mildew, but rather due to a chemical reaction between the
tannic acid in the wood and the metal in the screws. When done
intentionally, it's a technique known as "ebonizing".

Regardless of the cause, one solution would be to drill the holes
oversize and glue in plugs to fill the holes. Done properly, it could
create an interesting detail when the wood is reused.

Gordon wrote:
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