[Nhcoll-l] PTFE tape on jars

Tue Jan 14 10:42:54 EST 2014

Dear All,

The problem with applying tapes and sheets that are not designed to be part of the closure is that it easily could lead to even more evaporation than without. There are simply too much variables (lid type, thread, thickness/smoothness/tackiness/tear strength of tape/sheet, amount of wraps around rim/applied stretching, applied strength tightening lid, etc.) which probably lead more to failure than to success. We used in the past Parafilm (wax-based stretch foil) and were not very enthusiastic about its overall effectiveness.

The better quality screw-cap lids are provided with a (PTFE-faced LDPE foam liners) liner, which is fixed (glued with EVA) to the inner side of the PP lid which seems to prevent stress damage (by wrinkling, stretching or partly displacement) to the liner when tightening the lid.

Regards,

Dries
Andries J. van Dam, conservator

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From: nhcoll-l-bounces at mailman.yale.edu [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Dirk Neumann
Sent: dinsdag 14 januari 2014 8:32
To: John E Simmons; nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] PTFE tape on jars

Morning John!

I think (personal impression rather than something I could proof) that deterioration follows the concept "similar dissolves in similar" (I am not sure if this literally translation of the German "Ähnliches löst sich in Ähnlichem" is common in English, too):

Parafilm is a polyolefin wax which is not that stable against organic solvents, my impression is that if parafilm gets into contact with long-chained hydrophobic hydrocarbonates, especially vaseline / petroleum jelly, the parafilm wax starts to "melt" and turns into a smeary waxy stringing substance. This type of deterioration is also observed in combination with vacuum greases.

PTFE tape: we have a type of jar without threads, for these PTFE tapes failed completely. For use in combination with metal lids / threaded jars (as long as there is no way to get hold of the acid-resistant type of metal lids which have stronger liners), I would prefer the teflon inlays which also protects the lid against corrosion / chemical reactions triggered from condensation inside the jar.

Removal of old silicone grease: thanks for pasting Simon's very valuable link into this discussion! I never used silicon based greases in the collection after devastating results from my initial testing with various vacuum greases (dumping a chunk of the grease into our denatured alcohol and comparing stability after 1 year). Since then, I always use ("my" most favoured and most appreciated) Alsirol grease produced by a small company in Bamberg, Germany. Just hope they will never run out of production, but as this fat is food safe and of prevailled usage in small scale breweries in Upper Franconia, I am confident ;-)

To remove old silicone glue, you may also use (quite drastic, but works just fine) a drilling machine with a soft & fine brass-brush-attachment turning at moderate speed. Tried this methods with large old battery jars with good results after receiving this tip from aquarium hobbyists cutting & re-glueing large tanks. One needs to be well skilled in free-hand operating of drilling machines, especially in combination with fragile glass containers, of course, but it works pretty well and is very time efficient.

All the best
Dirk

Am 13.01.2014 18:43, schrieb John E Simmons:
Dirk,
Thanks for your contribution to this discussion. Just to be clear, the recommended use of PTFE tape is to wrap it around the threads on the jar before the lid is applied, in order to help the lid seal better with the jar.  PTFE is less permeable to the transmission of oxygen than Parafilm.

I presume that the deterioration of parafilm that you describe is caused by contact with the old grease remaining on the glass? Do you have any idea what the chemical reaction is that causes the deterioration?

The Teflon liners should work well--we can purchase several sizes of jar lids here with Teflon liners already in them.
Concerning the removal of old silicon, Simon Moore pointed out to me that you can purchase a silicon releasing agent in liquid or spray form at many hardware stores in the US and the UK. These work with the methyl groups in silicon:
http://www.dowcorning.com/content/discover/discoverchem/si-release.aspx?e=How+Silicones+Work
Since Simon alerted me to the release agent, I have used the liquid form to remove old silicon seals from glass several times--you might want to try a silicon release agent on the silicon oil you mentioned.
--John

On Mon, Jan 13, 2014 at 2:18 AM, Dirk Neumann <dirk.neumann at zsm.mwn.de<mailto:dirk.neumann at zsm.mwn.de>> wrote:
Dear Paul,

we had bad results with PTFE tape because it didn't seal jars adequately even though tied thoroughly around the lids.

Parafilm as Tony suggested works much better. You can easily remove it residue-free again, but be careful if wrapping parafilm around jars that are closed with ground stoppers / glass planes & grease (e.g. old battery jars): the parafilm will dissolve quickly into a rather sticky slime, which can hardly be removed.

For twist-off jars with metal lids adding additional Teflon liners to be inserted in the lids might be an idea: colleagues in Switzerland use those with pretty good results for several years now (the website is in German, they don't offer a English version, sorry - But from the pictures you may get an idea what those liners look like).
http://www.taxidermy.ch/p078000003.html?article_id=78000164&shop_action=detail

I am not sure if these are available in the US, but these liners not only seal but also protect metal lids against evaporating moisture thus preventing them from rusting.

For Le-Parfait jars etc. you can also add some high quality joint grease - but be careful and avoid any silicon based vacuum grease as it is nearly impossible to bring the silicon oil off the glasses after the silicon grease deteriorated (which happens within few years).

Hope this offers some ideas ...

All the best
Dirk

Am 10.01.2014 22:48, schrieb Callomon,Paul:
Folks,

At least 20 years ago (before my time here), white plumbers' tape was wrapped around the edge of the lids and onto the sides of all the bottle and jars in a certain section of our alcohol collections. This is the PTFE tape that plumbers use to seal threads; it is thin, soft and non-adhesive. Presumably the idea was to provide a secondary vapor barrier in addition to the jar lid seal.
We are now doing long-overdue major maintenance on this collection, and are trying to assess the efficacy of this tape. I'd be very interested to hear from anyone who (a) has used it and can show it works (b) has used it and can show it doesn't work, or (c) who considered using it but decided not to, and why.

Paul Callomon
Collection Manager, Malacology, Invertebrate Paleontology and General Invertebrates
________________________________
Academy of Natural Sciences of Drexel University, Philadelphia
1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA
callomon at ansp.org<mailto:callomon at ansp.org> Tel 215-405-5096<tel:215-405-5096> - Fax 215-299-1170<tel:215-299-1170>

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_______________________________________________
NHCOLL-L is brought to you by the Society for the Preservation of
Natural History Collections (SPNHC), an international society whose
mission is to improve the preservation, conservation and management of
natural history collections to ensure their continuing value to
society. See http://www.spnhc.org for membership information.

--

Dirk Neumann

Tel: 089 / 8107-111

Fax: 089 / 8107-300

email: Dirk.Neumann(a)zsm.mwn.de

Postanschrift:

Staatliche Naturwissenschaftliche Sammlungen Bayerns

Zoologische Staatssammlung München

Dirk Neumann, Sektion Ichthyologie / DNA-Labor

Münchhausenstr. 21

81247 München

Besuchen Sie unsere Sammlung:

http://www.zsm.mwn.de/ich/

---------

Dirk Neumann

Tel: +49-89-8107-111

Fax: +49-89-8107-300

email: Dirk.Neumann(a)zsm.mwn.de

postal address:

Bavarian Natural History Collections

The Bavarian State Collection of Zoology

Dirk Neumann, Section Ichthyology / DNA-Lab

Muenchhausenstr. 21

81247 Munich (Germany)

Visit our section at:

http://www.zsm.mwn.de/ich/
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