Betty Jean,
  There was a thread a few months ago dealing with archival materials and
cotton etching shell vials.  I believe Gary Rosenberg mentioned that on
looking through the collection at the Academy he did notices some etching
on the glass vials which were plugged with cotton.  I undertook an
unscientific review of the collection at the Carnegie Museum and looked at
some lots of terrestrial gastropods that are in glass vials and plugged
with cotton.  Of the 10 or 15 vials I looked at I saw no etching.  Cotton,
I believe, does come in different grades and purity and possibly that
which was used in the vials I checked might have been what we now would
consider as acid free. I do believe that some of the synthetics are now
preferred to cotton though in my collection I still use medicinal grade
cotton.  My vials are shell vials and the trays that I make are made from
acid free, low sulfur content paper and are buffered with calcium
carbonate.  My collection is stored in my basement and since I have been
using a dehumidifier, daily in the summer and 2-3 times a week in the
winter I have had no further problems with mold.
 
Charlie
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Charlie Sturm, Jr
Clinical Instructor - Family Medicine
  University of Pittsburgh School of Medicine
Research Associate - Section of Invertebrate Zoology
  Carnegie Museum of Natural History
 
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