[Nhcoll-l] Update on jar lid liner issue

[Hawks, Catharine]

Did Kohls note what was used as the blowing agent? I've seen many polyethylene foams that were blown with gases other than nitrogen that have discolored (yellowed) quite rapidly.

Scott, might this contribute to the deterioration of the liners in Paul's collection?

Cathy
Catharine Hawks
Conservator
National Museum of Natural History, MRC 106
Research & Collections, NHB 394
Smithsonian Institution
PO Box 37012
Washington, DC 20013-7012
Office 202.633.0835
SI Cell 202.701.8458
CH Cell 703.200.4370
hawksc at si.edu<mailto:hawksc at si.edu>


________________________________
From: nhcoll-l-bounces at mailman.yale.edu [nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Paul Callomon [callomon at ansp.org]
Sent: Wednesday, August 01, 2012 1:33 PM
To: NH-COLL listserv (nhcoll-l at mailman.yale.edu)
Subject: [Nhcoll-l] Update on jar lid liner issue

Colleagues,

Realizing the possible implications for us all of age-related failure of jar lid liners, I have been doing some survey work. The results are encouraging.


-          The supplier of the liners, O. Berk (KOLS Containers in those days) have confirmed that the liner in question is a generic version of the Tekniplex F217 liner that differs from the brand-name version only in the blowing agent that is used to foam the center core. The outer skins are solid low-density polyethylene, and the center is foamed LDPE.

-          I retrieved and tested several other jars using the same lid that were put into service in the same or following year (2000-01). The lids thus came either from the same batch as the failed one, or from another batch that was purchased shortly after. I carried out a simple visual examination followed by a pliability test. For the latter, I lifted the edge of the liner (it is glued to the inside of the lid) in two places using a dental hook and folded a flap over until it touched the surface of the liner (folded double). When it had returned, I inspected the surface. The material showed some wrinkling from this treatment, as is normal, but no cracking or crazing. This is the same thing that happens with a brand new liner, and although the wrinkling remains to a certain extent, this does not seem to compromise sealing.

-          By contrast, the failed liner snapped when folded over, and its surface is covered with a combination of fractal (branching) crazing as well as the cell-like crazing one sees in old ceramic glazes. The material has thus clearly undergone a major chemical change, and a colleague has generously offered to run tests to try and diagnose this.

In conclusion, it seems that this might have been a single incident. The next step is to trace the history of the contents (13 separate specimen lots in glass tubes) and see what treatments were used on them that might have caused this problem.


Paul Callomon
Collections Manager in Malacology, Invertebrate Paleontology and General Invertebrates
The Academy of Natural Sciences of Drexel University
1900 Benjamin Franklin Parkway
Philadelphia, PA  19103
callomon at ansp.org
Tel. 215-405-5096
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