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

Tue Jun 24 12:17:19 EDT 2025

Hi Marion,

Glycerol has been found to be an excellent preservative, taking in the extra caveats than Dirk and John S have highlighted.  Bear in mind too that a change from ethanol to glycerol involves a large change in osmotic pressure and specific gravity of the preserving fluid.  I would try this out at first with a few varied specimens to get experience as you will find that the specimens float for a while. There may be a way to overcome this?

This is a comparatively new technique, although Alizarin transparencies (diaphonised specimens) have been preserved in glycerol (with the fungus preventer crystal) for over 100 years I think, and that has worked very well.

Also, bear in mind that glycerol is a clearing agent, so you may get some transparency showing over time.

And, as Dirk says, fire prevention officers are nervous about using flammables in collections, particularly after the fire in Brazil where alcohol would have aided the combustion, and there are many myths surrounding this problem.  The only real problems with alcoholic preservatives are solvency of lipids &c, affecting the specimens over time and evaporation in my experience.

Hoping that this helps.

With all good wishes, Simon 

Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian.

www.natural-history-conservation.com

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> On 24 Jun 2025, at 16:38, Dirk Neumann <d.neumann at leibniz-lib.de> wrote:
> 
> Dear Marion,
> 
> there is this myth of "fire hazard" in exhibitions; maybe let's do some myth busting:
> 
> 1. I doubt that few small jars containing alcohol do harm (in terms of being a 'considerable fire risk'); dangerous good regulations-wise, ethanol up to 1 litre (in general, i.e. up to 98%) is not considered to be a fire risk, and is not IATA regulated. The exemptions for limited quantities are 5 litres.
> 
> 2. For creating a fire risk in an exhibition space, you would need to calculate the entire volume of ethanol vapour (not the total ethanol fluid volume) that would be needed to create a combustible ethanol atmosphere in this room. For a moderately sized exhibition room, this would be probably 100 litres or more that you would need to spill or suddenly "release".
> 
> 3. If the showcase is fixed e.g. to the ground or otherwise 'stable', i.e. cannot be accidentally moved or knocked over, how should it tip to allow this sudden release? Usually, you would need to knock off a larger wall installation or tank for creating a combustible ethanol atmosphere that is a considerable fire risk.
> 
> 4. And even if there would be a leakage or 'sudden release', where is the nearest potential ignition source that could cause an immediate ignition? Where are the nearest power plugs, are there risks from electrostatic discharges (e.g., because of the flooring)?
> 
> 5. Are visitors directly exposed to ethanol or formaldehyde fumes, i.e. are the jars a real health hazard (likely not - especially if they are permanently sealed)?
> 
> 
> My personal approach is (which is probably related with my long work at the airport, including DGR-handling): 
> 
> - know the limitations and be sure that you are below the allowances (knowing them is better than making good but wrong assumptions)
> - if your finding is "yes, we are above allowances", what are the risks we need to control, and how can we meet them
> 
> Maybe invite local firefighters and discuss risks and options with them - usually, they know the local regulations very well. They are probably regularly in your museum anyway for recurring fire-safety checks and give you more input and advice.
> 
> Would not move the specimens if there is no need to.
> 
> Hope this gives your further input ;-)
> 
> With all best wishes
> Dirk  
> 
> 
> Am 24.06.2025 um 16:13 schrieb Marion BILLOT:
>> 
>> 
>> Dear Dirk,
>> Thank you very much for your fast reply.
>> Yes, I am in contact with Marion Dangeon and Laura Brambilla, and I attended their training last week. It was actually they who pointed me in that direction. We have also carried out the sealing of the jars.
>> The issue here is not only about considering long-term preservation, but also the risk posed by the presence of ethanol or formalin in the display cases. It has been demonstrated that preservation in glycerol is not the most suitable method, but if we assume that the specimens have no scientific value and are intended solely for exhibition, then this type of fluid could be preferred. I also forgot to mention that it is recommended to add a few crystals of menthol to the glycerol to limit the growth of fungal organisms.
>> Thank you again !
>> Best regards,
>> Marion
>>  
>> <image.gif><image.gif>Marion BILLOT
>> Collaboratrice support scientifique
>> Invert?br?s
>> T. +41 22 418 6459
>> marion.billot at geneve.ch Mus?um d'histoire naturelle (MHN)
>> D?partement de la culture et de la transition num?rique
>> Route de Malagnou 1
>> 1208 Gen?ve
>> www.museum-geneve.ch<image.gif><image.gif>Notre environnement est fragile, merci de n'imprimer ce message qu'en cas de n?cessit?.
>>  
>> De : Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> De la part de Dirk Neumann
>> Envoy? : mardi, 24 juin 2025 15:55
>> ? : nhcoll-l at mailman.yale.edu
>> Objet : Re: [Nhcoll-l] [EXTERN] Glycerol as a safer alternative to ethanol for display specimens - Feedback from your practice?
>>  
>> Vous n?obtenez pas souvent d?e-mail ? partir de d.neumann at leibniz-lib.de. Pourquoi c?est important 
>> 
>> 
>> ATTENTION : Ce message provient d'un domaine de messagerie externe, soyez vigilant-e.
>> Dear Marion,
>>  in your specific case, it is worth considering a permanent seal for the jars, as you cannot avoid fluctuations of relative humidity in the exhibition (even though this might be mitigated by your display cases).
>>  Colleagues at the MNHN in Paris looked into (permanent) seals and sealants (there should be an article in the special edition of CoFo for the PFC conference in Paris), but there is also the group in Neuchatel ate the HE-Arc, which you probably know.
>>  Dries van Dam and Simon Moore also published on suitability of specimens in glycerin and surely comment ...
>>  Hope this helps
>> Dirk    Am 24.06.2025 um 15:40 schrieb Marion BILLOT:
>> 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
>>   <image001.gif><image002.gif>Marion BILLOT
>> Collaboratrice support scientifique
>> Invert?br?s
>> T. +41 22 418 6459
>> marion.billot at geneve.ch Mus?um d'histoire naturelle (MHN)
>> D?partement de la culture et de la transition num?rique
>> Route de Malagnou 1
>> 1208 Gen?ve
>> www.museum-geneve.ch<image003.gif><image001.gif>Notre environnement est fragile, merci de n'imprimer ce message qu'en cas de n?cessit?.
>>  <image004.jpg>
>> 
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>> _______________________________________________
>> NHCOLL-L is brought to you by the Society for the Preservation of
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>> natural history collections to ensure their continuing value to
>> society. See http://www.spnhc.org for membership information.
>> Advertising on NH-COLL-L is inappropriate.
>>  -- ****
>>  Dirk Neumann
>> Collection Manager, Hamburg
>>  Postal address:
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>> Leibniz Institute for the Analysis
>> of Biodiversity Change
>> Dirk Neumann
>> Martin-Luther-King-Platz 3
>> 20146 Hamburg
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>> www.leibniz-lib.de
>>  --
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>> 
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>>  --
>> Stiftung Leibniz-Institut zur Analyse des Biodiversit?tswandels
>> Postanschrift: Adenauerallee 127, 53113 Bonn, Germany
>> 
>> Stiftung des ?ffentlichen Rechts;
>> Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Gr?ter (Kaufm. Gesch?ftsf?hrer)
>> Sitz der Stiftung: Adenauerallee 160 in Bonn
>> Vorsitzender des Stiftungsrates: Dr. Michael Wappelhorst
> 
> 
> -- 
> ****
>  Dirk Neumann
> Collection Manager, Hamburg
>  Postal address:
> Museum of Nature Hamburg
> Leibniz Institute for the Analysis
> of Biodiversity Change
> Dirk Neumann
> Martin-Luther-King-Platz 3
> 20146 Hamburg
> +49 40 238 317 ? 628
> d.neumann at leibniz-lib.de
> www.leibniz-lib.de
>  -- 
> Stiftung Leibniz-Institut zur Analyse des Biodiversit?tswandels
> Postanschrift: Adenauerallee 127, 53113 Bonn, Germany
> 
> Stiftung des ?ffentlichen Rechts;
> Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Gr?ter (Kaufm. Gesch?ftsf?hrer)
> Sitz der Stiftung: Adenauerallee 160 in Bonn
> Vorsitzender des Stiftungsrates: Dr. Michael Wappelhorst
>  
> -- 
> Stiftung Leibniz-Institut zur Analyse des Biodiversit?tswandels
> Postanschrift: Adenauerallee 127, 53113 Bonn, Germany
> 
> Stiftung des ?ffentlichen Rechts;
> Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Gr?ter (Kaufm. Gesch?ftsf?hrer)
> Sitz der Stiftung: Adenauerallee 160 in Bonn
> Vorsitzender des Stiftungsrates: Dr. Michael Wappelhorst
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> 
> _______________________________________________
> NHCOLL-L is brought to you by the Society for the Preservation of
> Natural History Collections (SPNHC), an international society whose
> mission is to improve the preservation, conservation and management of
> natural history collections to ensure their continuing value to
> society. See http://www.spnhc.org for membership information.
> Advertising on NH-COLL-L is inappropriate.