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

Fri Jul 3 02:07:05 EDT 2026

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:

[cid:part1.jOs8jT76.U075wixS at leibniz-lib.de]

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

[cid:part2.80tveUdj.DbIkhuer at leibniz-lib.de]
________________________________
From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu><mailto:nhcoll-l-bounces at mailman.yale.edu> on behalf of Claire Smith <claire.smith at reading.ac.uk><mailto:claire.smith at reading.ac.uk>
Sent: 02 July 2026 16:22
To: nhcoll-l <nhcoll-l at mailman.yale.edu><mailto: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

[cid:part3.4djXjWXV.zO07FoVN at leibniz-lib.de]

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Stiftung Leibniz-Institut zur Analyse des Biodiversitätswandels
Postanschrift: Adenauerallee 127, 53113 Bonn, Germany

Stiftung des öffentlichen Rechts;
Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Grüter (Kaufm. Geschäftsführer)
Sitz der Stiftung: Adenauerallee 160 in Bonn
Vorsitzender des Stiftungsrates: Dr. Michael H. Wappelhorst
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