Collectors are also doing a great deal of research on plastics.  The National Button Society has a new publication with information on the use of plastics in buttons.  It may prove useful for distinguishing plastics that are breaking down, and includes information on heat testing with a hot needle tool to determine plastic type.  Information based on the chemical makeup of various plastics is included, and is being further diligently researched by several collectors.  Even tho it is published as a collector's guide, it may prove very helpful.
Howells, Jocelyn, Joan MacFarlane, and Nikki Deal
ND (2000)  National Button Society Section 9-A Synthetic Polymers Handbook.  National Button Society.

Susan Houghton
Burns & McDonnell, Inc.
Kansas City, MO 


>>> [log in to unmask] 09/12/01 10:32AM >>>
Regarding plastic buttons, I believe it would be foolish to totally disregard
them as a temporal dating tool. The clue is the chemistry of plastic, which
changed radically over the years. With the proper funding and archival
research, we could retain chemists to break down samples of plastic items
dating from bakelite, celluloid, and post World War II chemical breakthroughs
to create a wonderful time sequence for plastic artifacts. I learned this
while working on an assemblage of plastic artifacts recovered from Old Town
San Diego State Historic Park, 1979-1980. Chemists assured me the formulae
for plastic technology changes are distinct, well published, patented, and
sequential. The problem we faced in 1980 was that no funding agency was
willing to finance this research. Perhaps someone else out there has an
interest in pursuing this topic?

Ron May
Legacy 106, Inc.