[Nhcoll-l] PTFE tape on jars

[John E Simmons]

Dirk,
"Ähnliches löst sich in Ähnlichem" in English is "like dissolves like." Its
good to know the German phrase.

Thank you for your detailed speculation on the problems with parafilm. I
think we all agree that the Teflon liners generally work best, when they
are available.

Your comments remind me again how much the materials used to make metal and
plastic lids vary from one country or region to another. I have also
encountered these differences working with collections in Latin America.
The basic lesson is that the best solution to a problem for one collection
is not always the best solution for another collection. It each case, it is
important to understand the locally available materials, to know exactly
how the lids fit (or do not fit!) on the jars, and to devise good
strategies based on the materials you have to work with.

Silicon is another good example of a material that varies widely in its
composition. I try to avoid silicon greases for the reasons you have
explained.

In the US we can buy some silicon-based caulking compounds designed for use
around sinks or for outdoor application that work reasonably well to seal
jars. I have attached an MSDS for one such product (Spectrem) that I have
used to re-seal old battery jars.  Can you get similar products in Germany?
There is, of course, one serious caution--as Dries van Dam has frequently
pointed out, silicon is not as resistant to oxygen and water vapor
permeance as some other materials, but for many applications it is easier
to work with and replace.

--John
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