Folks,
  The discussion of the best packing material and recent discussions of
archival issues got me thinking.  One question that frequently has come up
and that several people have contacted me about is "what plastics are
considered archival?"  The answer is polystyrene, polyester,
polypropylene, polycarbonate and teflon.  The harder question is how to
determine which containers are made of these materials.  Sometimes it is
specified, sometimes not.  Quess what!  For some of them there is an easy
way, at least some of the time.
  Plastics that can be recycled are all marked on the bottom with a
triangle, a number and several letters.  These tell what plastic was used
in making the item.  I had a question recently about what 35mm film
containers were made of.  Someone on another list group told me that he
thought they were made of high density polyethylene.  When I looked on the
bottom of one there was the triangle with a "2" inside of it and the
letters HDPE below the triangle... the code for high density polyethylene.
  For those who are interested here are the 7 codes for plastics.
Remember the triangle contains the number and usually below it are the
letter abbreviation for the plastic.

1 - PETE...polyethylene terephthalate  = polyester  archival
2 - HDPE...high density polyethylene  archival
3 - V......vinyl/polyvinyl chloride  not archival
4 - LDPE...low density polyethylene  archival
5 - PP.....polypropylene   archival
6 - PS.....polystyrene     archival
7 - O......other all bets off as to what it is consider it not archival
While not all items are marked, many are and this should help some of us.
  Take care.
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History, Pittsburgh, PA
Assistant Professor - Family Medicine

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