Microwave drying

Thanks to Gregor Trinkaus-Randall and Gary Saretzky for revving me up enough
to to talk about microwaves and preservation.  Fair warning--I won't get
back to the original question about musty odor and mold for a long time.
Like many other preservation/ conservation ideas that seem to offer a fast,
cheap, universal solution to a common problem, this one has surprising
longevity. This strategy came out of experiments by a Professor Brezner at
the forestry school of a state university in New York.  My notes seem to
have stayed at NEDCC, so some details are foggy, but I talked to Dr.
Brezner at the time. He apparently discovered that a household microwave
provided a relatively cheap, clean, effective way to eradicate insect pest
supplies after experimental use. Apparently he talked this over with a
colleague in the industrial paper program, and they decided it would be
handy for libraries.  Dr. Brezner experimented and discovered that
microwaving did, indeed, kill bugs (I don't think species were reported) in
books and magazines he treated.  He offered a protocol that was published
in Library Journal.  I haven't read the TAPPI paper, which presumably gives
additional details.

Sherelyn Ogden and I gathered a small variety of (dry) bound materials and
followed Brezner's protocol (times, settings, procedure) using the only
insects readily to hand, ants (I still feel a little guilty).  We hollowed
out the interior of a small (~3x5") hard-cover, case-bound book; put in
some ants (species unknown, adults only); and cooked them.  They died.  It
can work for adult ants, if you have them in books.

Here are other things we observed:

    *   The c. 1987 AIC Directory was bound with thermoplastic
        adhesive.  It melted, and its pages detached, most of them
        individually, since when the adhesive cooled it no longer
        held them. (So much for the average paperback.)

    *   A copy of American Libraries, staple-bound through the fold,
        caused arc-ing. (So much for many serials.)

    *   The small case-bound book was printed c. 1870.  Its cover
        warped (which Brezner had predicted and Gary observed in his
        wet samples); unfortunately, unlike Brezner's sample(s), it
        didn't recover its original shape, and remained slightly
        cupped (we didn't press it).  More interestingly, it smoked,
        so we aborted the trial and discovered that pages had
        "toasted" around a point at the upper outer corner of a
        point centered at about 1/3 of way into the text block.  If
        we had left the book in the microwave, I assume it would
        have ignited, but we don't know if that would have happened
        before completion of the recommended exposure time. (So much
        for fire safety, 19th-c. paper, small hard-covers....) --
        Dr. Brezner told me by phone that he had observed none of
        these effects. He seemed miffed.

    *   Apparently household microwaves vary significantly in power,
        even within a single manufacturer and model number.  One
        would have to develop one's own times and settings, based on
        experience with a specific appliance

I didn't try to dry wet books, since it seemed hazardous and labor
intensive, and my frost-free freezer works a treat for small
quantities, although much more  slowly.  Gary's experience seems to
bear this out.  For a small number of damp items, air drying seems
to be the way to go.  This is also what I recommend for musty odor,
although there are many deodorizing strategies based on absorbents
and deodorants (baking soda, (clean) cat litter, charcoal,
potpourri, etc.) in an enclosed system.  I think drying and airing
are usually adequate, assuming there is no visible mold, and clean
material is going into a moderate environment.

Now to the real questions, which I've never been able to get
answered (and no, I haven't pursued it very seriously): I gather
that vacuum freeze drying will not kill mold spores.  Like VFD,
microwaving should kill live mold, since it contains and depends on
water.  Molecular excitation could heat the water enough to kill the
mold.  What about conidia?  What temperature is required to kill
"spores?" Once non-viable, can those spores still trigger allergic
responses?  What about mold-borne toxins?  Are they contained in
spores?  Do they remain active once the spore is no longer viable?
Thanks for any information offered,

Karen Motylewski
Director, Preservation and Conservation Studies
Graduate School of Library and Information Science
SZB 564/D7000, University of Texas at Austin
Austin, TX 78712-1276
512-471-8290
Fax: 512-471-8285

                                  ***
                  Conservation DistList Instance 11:39
                Distributed: Thursday, October 23, 1997
                       Message Id: cdl-11-39-002
                                  ***