[Nhcoll-l] [EXTERN] Re: Recommendations on ethanol use in natural history collections

Thu Apr 9 13:16:21 EDT 2026

Dear Annika and all

implementing regulation (EU) 2018/1880 of the European Commission gives a neat summary of the most common currently used denaturing agents. Keep in mind that some like the low boiling benzine petroleum ether (CAS 8032-32-4) - which in fact is not an ether - may not appear there, as it is no longer used.

Here is a link to the reg which is available in all languages of the EU: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:32018R1880

Most common (in Europe) is Methylethylkentone (MEK), and as taxation rules are harmonised throughout Europe, it would not be surprising if MEK is added in Norway as well. Additionally to MEK, the bitterant denatonium benzoate (bitrex, CAS 3734-33-6) is added. MEK is a very aggressive ketone and solvent that is also used in chromatography. MEK dissolves polystyrene and and used as a welding agent for polystyrene, it can break up and autoxidise into acetone, and is know to affect plastics such as PVC by breaking up the polymer chains.

Camphor has been frequently added in francophone countries, but is no longer on the list of approved EU denaturants as is an irritant. Ingested it is toxic, prolonged exposure to camphor vapours may cause dizziness or disorientation and may be toxic if respired in higher doses. Camphor is a natural resin and tends to stain specimens brownish to dark brown (if they are exposed for long time) - and is also used as an agent for browning or blackening.

Isopropanol (added in the UK, Sweden and Croatia) tends to embrittle tissues and ligaments, it is used as solvent, and may also oxidise to acetone.

In some countries in Europe, there are exemptions for natural history collections to use undenatured alcohol for their collection. If I recall correctly (others may correct me), this is the case in Switzerland, Italy and Sweden, but there may be more countries. Thus it might be worth checking.

MEK accelerates discolouration of specimens (see images on plate 7 D and E and plate 9 in our book); 7E is haemoglobinie leacheing from the gills of freshly transferred whitefish, right is a jar with African chlorophyll leached from herbivorous distichodus.

In many museum, alcohol specimens have a history of topping up, i.e. a large mixture of several denaturants that were 'added' over time which may cause unwanted secondary reactions. This is might be occasionally be the case if there is residual petroleum ether, which may at a sudden turn cloudy when topping up with MEK denatured alcohol.

Hope this helps and offers some orientation.

With best wishes
Dirk

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Am 09.04.2026 um 17:36 schrieb Ian Engelbrecht:
ACHTUNG/ATTENTION: Diese E-Mail stammt von einem externen Absender. / This e-mail comes from an external sender.

I'm interesting to hear about this too, the question of using 'denatured' ethanol for long term specimen preservation. We have a similar situation here in South Africa - standard ethanol is prohibitively expensive because of a tax levied on it, essentially so that people don't buy it to drink. In order to get around paying that tax you have to register with the national taxation body, which is exceedingly difficult to do, even if you are a large national museum or other institution. Many people are falling back to 'denatured' ethanol, which typically has another compound added to make it undrinkable.

I'd imagine the question of the impact on specimens depends on what the ethanol is denatured with. Most often (here) it's isopropyl alcohol, but sometimes it's ethyl acetate. In both instances we don't actually know what the long term implications are for specimen preservation. Ethyl acetate, for example, might make specimens very brittle. Bleaching might be another concern.

Furthermore, these added compounds are unpleasant to work with. People describe feeling light headed, or even getting headaches, from prolonged exposure. There might be more serious health implications too.

Ian

On Thu, Apr 9, 2026 at 2:58 PM Nickson Otieno <neotieno at gmail.com<mailto:neotieno at gmail.com>> wrote:
Just a little point, that for any specimens from which that you might later wish to derive tissues for purposes of stable isotope analyses, preservation in ethanol of any kind, would significantly distort the isotooic signatures (particularly for the case of isotopes of nitrogen).

Nickson Otienio
National Museums of Kenya

On Thu, Apr 9, 2026 at 3:20 PM Annika Sander <annika.sander at vestfoldmuseene.no<mailto:annika.sander at vestfoldmuseene.no>> wrote:
Dear colleagues,
I am seeking specific recommendations regarding the use of undenatured ethanol for wet specimens, as well as references addressing any potentially harmful effects of denatured ethanol on such specimens.
The background is as follows:
We are a regional museum in Norway with an important collection of wet specimens, particularly whale foetuses and other specimens related to whaling. As is common in wet collections, our specimens gradually lose preservation fluid over time. In order to replenish the jars, we need to procure undenatured ethanol.
In Norway, this type of ethanol is subject to specific taxation regulations. To be registered with the relevant authorities and obtain access, we are required to provide documentation demonstrating the necessity of using undenatured ethanol. This is further complicated by the fact that we are not a university, laboratory, or scientific institution, which would otherwise have more straightforward access to such materials.
Previously, a taxidermist carried out the refilling and transfer from older preservation fluids to ethanol, but this is no longer an option.
Any recommendations for relevant literature or other guidance on how to deal with this would be greatly appreciated.

Kind regards,

Annika Sander,

Conservator (wood and furniture)

Dep. Archives and Collections

phone: +47 981 87 851

e-mail: annika.sander at vestfoldmuseene.no<mailto:annika.sander at vestfoldmuseene.no>

Vestfoldmuseene IKS

www.vestfoldmuseene.no<http://www.vestfoldmuseene.no/>

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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
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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.

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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.

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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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