Chris Hogg wrote:
On Sun, 12 Jun 2016 11:28:51 +0100, "Dan S. MacAbre"
wrote:

I discovered that acetone is rather good at getting rid of the paint
that lingers in wood grain after the more heavy-duty stripping, which I
find always leaves a bit behind. So I now have nice (if slightly
distressed-looking) bare wood window sills again. Unfortunately, I left
some tools on there overnight, and they have left a black mark (looking
a bit like exposed photographic paper) where they contacted. Is this a
known phenomenon? It would seem to be a good wood stain. And (more to
the point), before I get the sandpaper out, is there a non-destructive
way to neutralise it?

Not sure it's got anything directly to do with the acetone, but iron
(e.g. nails, or in your case, tools) is notorious for staining wood,
especially oak. It's the tannin in the wood that reacts with the iron
to give a black stain, presumably some sort of iron tannate. IIRC
moisture is involved somewhere; did it rain, or was there a heavy dew
overnight? I expect you'll tell me they were indoors! Don't know a
solution. Perhaps spread some iron filings over the rest of the cill,
and at least get it all a uniform colour!


Okay, that seems like the answer. It /is/ indoors, but maybe the
acetone had some water in it (it is described as 98%). The marks are
left by the edge of one of those triangular paint-stripping things, and
the bottom of a nitromors can, so there is going to be some iron in
there. I'll probably just sand it out - it will add to the distressed
look that the missus currently likes.