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Re: [BKARTS] Dry rot



From:   "Gavin Stairs" <stairs@xxxxxxxxxxxx>
Subject:        Re: Books and Humidity


Gavin Stairs asked:  "Why is it called dry rot when it depends on
humidity?"

If I correctly remember my classes on biodeterioration from U.C.
Berkeley, "dry rot" refers to a specific form of fungal attack on
wood by specific organisms, in which the metabolism of the fungus
produces sufficient moisture for it to spread and destroy the wood.
The fungus does need moisture to grow, as do all common fungi, but
once it is established it can produce its own moisture. In
consequence, dry rot can be found in microclimates which are
otherwise dry. If I remember correctly the fungi involved will also
thrive in wet microclimates, and indeed need external moisture in
order to become established; it is only after they are established
that they can produce their own moisture.

To the best of my knowledge and belief the term "dry rot" is not used
for a form of book or paper decay by bonservators or biologists, and
I would be very interested to see citations using the term from
relevant technical or professional literature. Of course, if books
are left in contact with dry-rotted wood one must anticipate spread
of the fungus into the book; many forms of biodeterioration  prefer
wood as their substrate but will make do with paper.

It is a great pity that this query was not answered by someone whose
knowledge is a little more recent than mine, or who is writing from a
site with relevant textbooks to hand. Some of the answers to Mr.
Stairs' question were distinctly odd. I am particularly irritated by
the notion that the term "dry rot," usually reserved for a form of
fungal decay, can be applied to "acid" deterioration in paper,
apparently merely because it is "dry." When paper is attacked by
acids (please note the plural: chemical attack on paper is by
specific compounds, not by some amorphous "acid") this is a form of
chemical attack, whether from manufacturing residues, from air
pollution, or other external sources. While dry rot completely
destroys wood, leaving gaps in the material, "acidity" in paper
embrittles it but does not completely destroy it. There also seems to
have been some confusion with "red rot" in leather, another specific
form of chemical decay: this slow but unstoppable reduction of the
leather to reddish powder is caused by residual sulfuric acid from
the manufacture of leather (specifically from the initial steps in
preparing the skin or from dyeing, but not from tannage itself), or
sometimes from sulfuric acid as a reaction product of the tannage
with sulfur dioxide air pollution. I would, again, be very interested
in citations from relevant technical literature of use of the term
"dry rot" for chemical rather than biological deterioration.

Tom Conroy
Berkeley



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