Folks-

I have a curious potential problem on my hands and hope that one of you
might be able to provide some input on the situation.

Many of our artifacts are curated in a climate-controlled room in very
tight cabinets. Within the cab's many of the individual artifacts are
enclosed in zip-top 4 mil thick polyethylene bags. Over the years we have
noticed that some of the bags and the paper tags inside them have turned a
yellow/green, especially, but not limited to, where the artifacts are
touching them. This process can take as little as 4 months. The artifacts
are composed of siltstone, quartzite, chert without matrix, basalt, shell,
and Chupadero sherds. One of the most curious things about this is that in
a collection from the same site, made at the same time, presumably
processed in the same manner, and re-housed 10 years ago using the same
types of materials, four artifacts of a given material will be fine and the
fifth will have turned the bag and tag color. The materials are from
Maverick, Val Verde, and Brewster counties in Texas as well as from up
around Carlsbad Caverns in NM.

My concern is not only for the artifacts themselves, but for the organics
that are curated in the same cabinets, especially since the housing is not
conducive to allowing gasses to escape. My plan is to get readings from
inside the offending bags with a mass spectrometer/gas chromatograph  to
see what shows up, but I would certainly appreciate any other information
or direction any of you could give me.

Thanks,
Laura Nightengale
Head of Collections
Texas Archeological Research Laboratory
The University of Texas at Austin
512-475-6853

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