[Nhcoll-l] [EXTERN] Re: Tips for tiny jars?

Tue Jul 7 05:57:29 EDT 2026

Hi Claire,

in addition to all of these good advices I would consider using 
previously heated lids, to create a internal negative pressure in the 
jars which will hold the lid on its place. This is very easy with 
cylindrical flanged jars. The surfaces have to be perfectly flat though. 
So it could be necessary to grind the flange and lid on a glass-plate 
with some silicon carbide (carborundum). As an adhesive you can use any 
of the recommended bellow (tar, gelatin, beeswax/rosin mixes, vacuum 
grease), depending on the preservation fluid of course. Place the 
adhesive on the cold flange and then press the heated lid (at least 90 
°C) on top. The heat will melt the adhesive and the negative pressure 
hold the lid on its place very nicely, creating an airtight sealing.

There is also a more careful approach that is completely non-invasive. 
Place the container in its current state in a much bigger container with 
a better seal, as proposed by John, but not just the specimens, but the 
whole jar, so the evaporation-rate is considerably minimized. Of course 
here you will need a good sealing too. Basically but the specimen jar in 
a empty jar. Its not a perfect solution, but it could slow down 
considerable the degradation process and preserve the whole integrity of 
the current specimen and jar.

All the best!

Am 03.07.26 um 08:07 schrieb Dirk Neumann:
> Hi Clare and all,
>
> what you describe sounds to me as if the sealant, either Gelatine or 
> the silicone, would not properly adhere to the ground surfaces on the 
> lid and neck. Also - at least judging from your photo - it seems that 
> the glass lid is smaller than the flange of the cylinder, which 
> reduces the adhesion surface: on the right side, it looks like the 
> glass cover sits in the middle of the ground surface of the neck. The 
> lid should always be slightly larger than the jar, the ground surface 
> of the glass closure wider than that of the neck. If the glass closure 
> is without ground surface, the sealant cannot adhere properly to the lid.
>
> For flanged jars, you need  a clean and sufficiently wide (large) and 
> even surface for the sealant to allow proper adhesion. The adhesive 
> itself should be impermeable for gas - or at least as impermeable as 
> it can be. The higher the sealant layer in this specific case, the 
> worse is the seal. Using 'more' does not make a better seal.
>
> Most silicones are a really bad choice, because they are not only a 
> bad gas barrier, but also leave silicone oils on the glass surface 
> that need to be removed with acetone or similar solvents. If the 
> silicone oil is not removed before resealing, the sealant has not 
> adhesion to the glass surface. Aquarium people probably know this 
> problem quite well...
>
> Gelatine seals can attract water vapours, and might also not be the 
> best choice. Gelatine seals can last long, but often they don't.
>
> My advice for your display jars would be - depending on the climate 
> conditions in the room they are stored in - to close the jars with a 
> high quality, silicone-free vacuum joint grease. The layer should be 
> as thin as possible. Build up a slight rim on the ground surface of 
> the lid, and carefully - with very light pressure - turn the closure 
> back and forth on the neck, until the grease film turns transparent, 
> which indicates a proper sealing. Close the jars in a room that is 2-3 
> °C warmer then the temperature in the storage room, to support slight 
> negative pressure to build up in the jar. Leave the jar in the storage 
> room for 2-3 days, then check the lid and slightly turn the glass 
> closure again, if the film got opaque and is no longer transparent. I 
> have used Alsirol with very good results. It can be easily removed 
> 'dry' with toilet paper, without leaving traces on the ground surface.
>
> For jars with display specimens, it is also worth considering a 
> permanent seal, Simon put some information on his website from his 
> course. Tar, or bees-wax-based seals would be a good choice to my mind.
>
> https://www.natural-history-conservation.com/FluidPreservationTechniques.pdf
>
> Hope this helps
> Dirk
>
>
>
> Am 02.07.2026 um 17:44 schrieb Claire Smith:
>> Apologies all, for the lack of clarity — I'm talking about old glass 
>> cylinders with a flat glass lid like this one:
>>
>>
>> Best wishes,
>> Claire
>>
>> *******
>>
>> *Claire Smith *(she/her), AFHEA
>>
>> *Postdoctoral Research Associate, Cole Museum of Zoology*
>>
>> University of Reading
>> _claire.smith at reading.ac.uk_ <mailto:claire.smith at reading.ac.uk>
>>
>> _www.linkedin.com/in/wetconservatrix_ 
>> <http://www.linkedin.com/in/wetconservatrix>
>> Social media: @wetconservatrix
>>
>> ------------------------------------------------------------------------
>> *From:* Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> on behalf of 
>> Claire Smith <claire.smith at reading.ac.uk>
>> *Sent:* 02 July 2026 16:22
>> *To:* nhcoll-l <nhcoll-l at mailman.yale.edu>
>> *Subject:* [Nhcoll-l] Tips for tiny jars?
>>
>> 	
>> External email: Treat content with caution.
>>
>>
>> Hi everyone (with apologies for cross-posting),
>>
>> We have a selection of small specimens in our fluid collection, in 
>> jars of around 10 to 25 mL, and they evaporate incredibly quickly. We 
>> have to top them up almost annually, which isn't great for the 
>> specimens. The rate of evaporation doesn't seem to be worse with a 
>> particular fluid, or with a particular sealant.
>>
>> Do those of you who work with fluid collections have any tips for how 
>> to prevent these tiny jars from evaporating so quickly?
>>
>> Best wishes,
>> Claire
>>
>> *******
>>
>> *Claire Smith *(she/her), AFHEA
>>
>> *Postdoctoral Research Associate, Cole Museum of Zoology*
>>
>> University of Reading
>> _claire.smith at reading.ac.uk_ <mailto:claire.smith at reading.ac.uk>
>>
>> _www.linkedin.com/in/wetconservatrix_ 
>> <http://www.linkedin.com/in/wetconservatrix>
>> Social media: @wetconservatrix
>>
>>
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>
>
> -- 
>
> ******
>
> **
>
> *Dirk Neumann*
>
> Collection Manager, Hamburg
>
> Postal address:
>
> *Museum of Nature Hamburg*
> Leibniz Institute for the Analysis
>
> of Biodiversity Change
>
> Dirk Neumann
>
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>
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>
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> natural history collections to ensure their continuing value to
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