Jars for biological specimens

Alayne Alvis <alayne.alvis [at] sydney__edu__au> writes

>We are not able to transfer the specimens into newer, better sealing
>jars; so we are now in the process of removing silicone sealer and
>replacing the ethanol solution. In order to reduce evaporation, we
>have been tying Parafilm M film over the jars and stoppers.
>Recently, after a record heatwave, we have noticed splitting of the
>Parafilm in areas of mechanical stress (where stretched over hard
>edges).  We feel that the roll of Parafilm we were using may have
>been heat affected and it finally failed in the extreme heat.
>
>We are investigating replacing the Parafilm with DuraSeal lab film
>as it has better heat resistance, but it has suggested that we
>resume using petroleum jelly. I am reluctant to use it considering
>previous experience.

I sympathise with your situation--a combination of poorly-fitting
lids and heat with ethanol preservative is challenging. The wax
films do not do so well in heat over hard edges and will split in
time.  There is another film produced by Mitsubishi but it will also
fail in a like manner.  The newer formulation of Parafilm (which I
buy from florists) works well but we don't experience such heat
levels in England.

PTFE tape (plumbers' tape) has also been tried here with some
success.  Another useful sealant, if available in tape form, would
be EPDM  (ethylene propylene diene Monomer).

Most silicone sealants do quite well in heat if they are applied
correctly (onto totally dry surfaces and then the jar topped up once
the silicone has cured, using a syringe through a filling hole) and
will reverse with silicone reversing agents.

There are other greases available which should do well but beware of
applying too much to the lid edge--just a smear is enough and once
the ground glass surfaces feel lubricated then the seal should last
and should not melt down into the preservative--it depends on the
size of the gap between lid and jar.  The two greases that I use are
Paraffin Soft White, available via VWR international and Alsirol
(from poellath.de).  If you ask the latter company, they should
supply a few free samples.  Petroleum jellies tend to 'pill' in
contact with alcohol and are less reliable, even if used to the
correct amount.

Some years ago, 3M also developed a sealing tape, with the help of
two Canadian researchers, but this was intended for screw-top jars.
Finally, your budget might stretch to purchase some new jars with
ground glass stoppers for the more important specimens or those with
really badly fitting lids and would save much staff time and worry
in the longer term.

In the UK we have

    <URL:http://www.dixonglass.co.uk>

who supply these.

I have not tried the Dura Seal lab film and would be interested to
hear of your findings should you try it.

My apologies for so many suggestions but I am hoping that someone
else in a hot country may see this, be able to extrapolate and
narrow the field for you.

Simon Moore MIScT, FLS, ACR
Conservator of Natural Sciences
20 Newbury Street
Whitchurch RG28 7DN


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                  Conservation DistList Instance 24:39
                Distributed: Saturday, February 19, 2011
                       Message Id: cdl-24-39-003
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