If its iron, I wonder if a magnet might be useful? Just a thought.
Brian

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The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Chris Hogg" wrote in message
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On Wed, 22 Jun 2016 08:35:02 -0700 (PDT),
wrote:


Well, the Oxalic acid worked brilliantly for a day or three, but the
brown stains have reappeared over the course of two or three weeks. The
stains seem to be more "spread about" and less intense than they were
before.

We just re-treated with Oxalic again this weekend and again, the brown
stains all disappeared within a few minutes. I imagine that the stains
will come back, hopefully less intense again. This could be a longish
term project to gradually get rid of the stains.

I know this is about 6 years ago now, and the chances of anyone seeing
this are slim, but did this eventually work for you? I am in a similar
situation.

I would suggest that after you've applied the oxalic acid (if you're
going down that road), flush it well and repeatedly and rinse away the
flushings, otherwise the iron, which is the cause of the staining,
will just return, if a little spread out and lighter, as the OP found.

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Chris