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

[Simon Moore]

Very interesting about the definition of denatured reacting to preserving alcohol.  

I have always favoured ‘adulterated’ but this term was not generally taken up.

With all good wishes, Simon 

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

www.natural-history-conservation.com



> On 9 Apr 2026, at 19:55, JP Brown <jpbrown at fieldmuseum.org> wrote:
> 
> Normally “denatured” means alcohol that has been refined to over 95% (the limit of distillation) by the addition of chemical dehydrating agents that carry off the remaining water.>
> 
> Not to hijack the thread, but I don't think this is correct, Paul. Denatured alcohol (in the US) is ethanol with a bittering or poisoning agent added to it to render it unfit for human consumption. This is the same idea as methylated spirits (in the UK and Commonwealth) - see, for instance, https://en.wikipedia.org/wiki/Denatured_alcohol.
> 
> JP
> 
> JP Brown (he/his)
> Senior Conservator
> Vice-Chair MFT-IDG
> 
> Field Museum
> 1400 S. DuSable Lake Shore Dr.
> Chicago, IL 60605
> fieldmuseum.org
> 
> 
> 
> 
> 
> On Thu, Apr 9, 2026 at 1:33 PM Callomon,Paul <prc44 at drexel.edu> wrote:
> Normally “denatured” means alcohol that has been refined to over 95% (the limit of distillation) by the addition of chemical dehydrating agents that carry off the remaining water. What folks are talking about here, however, is “methylated spirits” and other forms of alcohol that have been deliberately poisoned to make them undrinkable. 
>  Isopropyl (rubbing alcohol) is not a bad long-term storage agent, and does preserve DNA, but it can shrink and harden specimens, often to the point of making dissections very difficult. It’s also not the nicest stuff to work with. 
>  If your country won’t let you easily buy ethanol, though, you might be better off going with Isopropyl than with some adulterated formula. 
>   Paul Callomon
> Collection Manager, Malacology and General Invertebrates
> Academy of Natural Sciences of Drexel University, Philadelphia
> 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 Ian Engelbrecht
> Sent: Thursday, April 9, 2026 11:36 AM
> To: Nickson Otieno <neotieno at gmail.com>
> Cc: Annika Sander <annika.sander at vestfoldmuseene.no>; nhcoll-l at mailman.yale.edu
> Subject: Re: [Nhcoll-l] Recommendations on ethanol use in natural history collections
>   External.
> 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> 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> 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
>   Vestfoldmuseene IKS
> 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
> 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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> _______________________________________________
> 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.