The Smithsonian uses glass lids held in place with the traditional fruit canning mechanism: a rubber 
gasket and a pressure seal applied with the metal lever lock. Though the teflon covered threads 
sounds promising...

Britt

Bruce Bartrug wrote:
> Catherine Bursh wrote:
> On the tape subject.... Anyone know the correct tape to use to seal the
> lids of specimen jars with alcohol in them? I'm tempted to use black
> electrical tape but not sure if the alcohol fumes will mess with the
> glue on the tape.
> The purpose of the tape is to slow the evaporation that takes place even
> with a threaded top.
> 
> Catherine, I have two suggestions for you -- neither of which, however, 
> I've actually tested for the purpose you indicated.
> 
> The first is teflon plumbers' tape.  Which is not really tape per se (it 
> has no adhesive) but is simply a thin film of a very inert and useful 
> material.  One wraps the tape on the threads to be sealed and tightens 
> the lid.  Very good at sealing the slightest leaks, even in gas lines.  
> I used it many decades ago to seal brass joints in gas lines for 
> chromatographs -- a instrument used to analyse chemical substances.  Try 
> to find some wide enough to fit the threads in question.
> 
> The second is a type of seal used to seal lids of packaged chemicals.  
> It's a circular sleeve of shrink-wrap type material that one positions 
> around a jar or bottle lid and then shrinks with a hair-dryer.
> 
> As I said, I've not tested these specifically for the application you've 
> mentioned, but I strongly suspect using both would significantly reduce 
> alcohol evaporation from a speciman container.  I'm suspecting you're 
> already using glass jars and metal lids?
> 
> /Suerte/,
> Bruce
>