[Nhcoll-l] Glycerol as a safer alternative to ethanol for display specimens - Feedback from your practice?
Fabian Neisskenwirth
info at naturhistorische-konservierung.de
Fri Jun 27 04:57:06 EDT 2025
Dear Esther, dear Marion,
Sorry for the late response, very interesting topic indeed.
I have transferred a few collections into glycerol with very good
results (i'm currently working on another collection doing this at the
moment). My first try was done by a simple protocol that I got from
Andries van Dam back in 2018, after he presented the use of Glycerol as
a alternative preservation fluid at the PFC2018 in Paris. The use of
glycerol goes back to the times of Carl Kaiserling (1869-1942) and
Leonhard Jores (1866-1935), both German pathologists that presented
their potential as preservation fluid over 120 years back in the field
of anatomical preparation. Besides a few publications from Andreis van
Dam (Maclead & Van Dam 2011; Van Dam 2020), there is not much resent
research into this mater that i'm aware of. I will hopefully be able to
publish something in a soon future. Andries and I did a nice
presentation at a meeting organized by the German conservators/restorers
society (VDR) last year, but there is no real conference paper available.
The glycerol solution concentration is crucial, specimens have to be
transferred into a 65% solution of glycerol in water. By this, the
mentioned absorption of humidity is inhibited since the solution is
"saturated" with water and there should be no absorption of water from
the environment. Glycerol solution with much higher content of glycerol
(80-95%), can indeed absorb moisture from the surrounding environment,
specially if poorly sealed. But if the transfer in steps into 65% of
glycerol is made correctly, there is no need for any kind of fungicide
in the preservation fluid. This is actually the biggest advantage of
using glycerol in the first place (besides fire hazards, toxicity issues
and/or evaporation), since it enables the use of a toxin free
preservation fluid. Cleared specimens stored in higher glycerol
concentrations, can be transferred into a 65% glycerol solution as well.
Other mentioned issues like the slight color change, are of course
things to be taking into account before the transfer. Besides that it is
a really sticky job.
Important things to take account are: big specimens that will take a
long time to transfer from one step into another; a very good plan of
transfer between fluids, since specimens will take different amount of
time to transfer depending on their volume; the size of the receptacles
for the transfer, since a good transfer requires a much higher ratio of
fluid to specimen in order to enable a fast diffusion of the fluid; and
of course the final container, since a good sealing is essential for the
preservation of fluid preserved specimens.
I would be super happy to provide you with a protocol, even tough this
has to be adapted to the specific collection, depending on specimen
size, tissue type and so on. Just let me know.
All the best,
Literature cited:
Van Dam, A.: Finding a cure for hazardous collections: the road to zero
formaldehyde and ethanol. In: Collection Forum (34). 2020. S. 118–123.
Macleod, I.; Van Dam, A.: A migration mechanism for transfer of sharks
from ethanol to aqueous glycerol solutions. Conference Paper. ICOMCC
Lisbon 2011.
Am 24.06.25 um 16:23 schrieb Esther Dondorp:
> 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>:
>
> 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> 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
>
>
> 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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> Natural History Collections (SPNHC), an international society whose
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> natural history collections to ensure their continuing value to
> society. Seehttp://www.spnhc.org for membership information.
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--
*Fabian Neisskenwirth*
Restaurator/Präparator
Waterfohrstr. 20
DE-45139 Essen
Tel: +49 (0) 1573 2778729
www.naturhistorische-konservierung.de
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