[Nhcoll-l] Glycerol as a safer alternative to ethanol for display specimens - Feedback from your practice?

Tue Jun 24 10:54:02 EDT 2025

Another consideration is the optical clarity of glycerol versus ethanol, both initially and over time. These are display specimens, so it seems a good idea to ensure that whatever medium you use has full-spectrum visibility and is stable over time (and under lighting) in that regard. Also, exudates from the specimens (like lipids) might discolor different fluids to differing extents.

Paul Callomon
Collection Manager, Malacology and General Invertebrates
________________________________
Academy of Natural Sciences of Drexel University, Philadelphia
callomon at ansp.org<mailto:callomon at ansp.org> Tel 215-405-5096 - Fax 215-299-1170

From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Esther Dondorp
Sent: Tuesday, June 24, 2025 10:23 AM
To: John E Simmons <simmons.johne at gmail.com>
Cc: nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] Glycerol as a safer alternative to ethanol for display specimens - Feedback from your practice?

External.
Dear all,

I was following your conversation out of interest and I am curious why you would not want to add a biocide to scientific specimens? Is it damaging? I ask this because we have our largest specimens in a tank in glycerol, because ethanol was no option (in terms of fire hazard and health and safety). And we added a lot of thymol to keep mold out...Also all the 'cleared and stained' specimens in the collection all have some biocide added to them.

Thanks!

Esther Dondorp
Collectiebeheerder reptielen, amfibieën en vissen
absent on Wednesdays
Monday, Tuesday, Thursday, Friday
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Op di 24 jun 2025 om 16:12 schreef John E Simmons <simmons.johne at gmail.com<mailto:simmons.johne at gmail.com>>:
I agree with Dirk--without a very good seal on the containers, the glycerol will likely absorb moisture from the air, introducing both airborne contaminants into the containers and possibly causing them to overflow (I have had both happen to containers of specimens in glycerin that were not properly sealed).

Because these specimens do not have scientific value, you should also consider adding a biocide to the glycerol such as a few crystals of thymol or a bit of camphor (as recommended by Simon Moore).

--John

John E. Simmons
Writer and Museum Consultant
Museologica
and
Investigador Asociado, Departamento de Ornitologia
Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima

On Tue, Jun 24, 2025 at 9:40 AM Marion BILLOT <Marion.Billot at geneve.ch<mailto:Marion.Billot at geneve.ch>> wrote:
Dear colleagues,

I am currently working on an exhibition project involving fluid-preserved specimens, and I am exploring the possibility of replacing ethanol with glycerol for long-term display purposes. The main objective is to reduce fire hazards and mitigate health risks in display environments (cases that are not airtight).

I am preparing to present this proposal internally. As this practice is not yet established in my institution and tends to raise concerns, I would be very grateful for any feedback from professionals who have experience using glycerol in this context.

To clarify:
·   The specimens are of strictly pedagogical value, they are not scientifically rare or culturally significant.
·   We aim for long-term display in semi-sealed cases with limited air exchange.
·   I understand that transferring specimens from ethanol to glycerol requires several days of transitional baths in demineralized water to avoid osmotic shock and tissue damage. I am considering a gradual transition: ethanol 70 % → 50 % → 30 % → 10 %, followed by glycerol in increasing quart-step dilutions. I will let it in a minimum of 4 hours for small specimen (5 cm).

Have you used glycerol for display purposes in your institution? If so, under what conditions, and with what types of specimens? Any technical advice, protocol suggestions, or reference materials would be most appreciated.

Thank you very much in advance for your insights. They will be very helpful in supporting a safer and more sustainable exhibition strategy.
Best regards,

Marion

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Marion BILLOT
Collaboratrice support scientifique
Invertébrés
T. +41 22 418 6459
marion.billot at geneve.ch<mailto:marion.billot at geneve.ch>
Muséum d'histoire naturelle (MHN)
Département de la culture et de la transition numérique
Route de Malagnou 1
1208 Genève
www.museum-geneve.ch<http://www.museum-geneve.ch/>
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