Yellowing of polyethylene bags

Laura H. Nightengale <lnightengale [at] mail__utexas__edu> writes

>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.

Could your bags be polyvinyl chloride (PVC) bags, which contains
Chlorine, rather than polyethylene bags? Our PVC bags do yellow
after years of use.

Alice Tsang


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                  Conservation DistList Instance 15:64
                 Distributed: Thursday, March 21, 2002
                       Message Id: cdl-15-64-005
                                  ***