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[BKARTS] Thymol/foxing

First off, yes, thymol is suspected of being a carcinogen and
possibly a mutagen (women of childbearing age should probably
avoid its use) but it is also one of the active ingredients of
Listerine mouth wash (0.06%; alcohol 26.9%; and a number of
other ingredients).

While it may be a problem, esp. for some, at low concentrations
it does not seem to be a serious problem.

Foxing can arise from the papermaking process (actual iron/steel
or bronze bits chipped off the machinery, or dissolved iron
in the water used in the beater) or from spores absorbed by
the paper.

With experience, these various sorts of foxing can generally be

Peter's basic advice about 50 %RH (or somewhat lower) where the books
are shelved/stored is the main thing one can do to stop foxing.

Removal of foxing is neither simple nor easy.

If it is mold-based and light, the book may be pulled apart and
bleached to remove it.  This sterilizes the paper, which is
good; it also destroys the sizing and that is not so good.  So
the book should be re-sized before re-binding.

If the mold-based foxing is heavy it will probably not be possible
to do more than lighten it by bleaching.  Going too far will destroy
the paper.

If the foxing is iron-based, bleaching only converts the stains to
a colorless iron salt and diffuses if further into the paper.

This means that if the book is later exposed long enough to high
levels of relative humidity the foxing will return and be worse
than before.

And bleaching weakens the paper.

For that reason I don't bleach books.  If a badly foxed print comes
into the lab I'll bleach it, because it will go back into a frame and
not be handled as a book is handled, so strength is not the main issue.


Thompson Conservation Lab.
7549 N. Fenwick
Portland, Oregon  97217

503/735-3942  (ph/fax)


"The lyfe so short; the craft so long to lerne."
Chaucer  _Parlement of Foules_ 1386

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