[Nhcoll-l] Alcohol concentration for terrestrial vertebrates

[Simon Moore]

Thanks John and Tonya,

What John says is true about the staging of alcohols and the final concentrations.  80% was what I was advised at the NHM in London when I worked there and by the time larger terrestrial vertebrates ‘end up’ in 80%, you will often find that with the mix of lower grade alcohols from the staging process, once things have settled down / equilibrated, then the net result is around 70% anyway.  Higher grade alcohols  can lead to embrittlement of certain tissues as well as evaporation issues.

I have also found the staging process necessary for the more fragile specimens as they undergo changes in Osmotic pressure during this process which can cause syneresis or shrinkage in softer tissues.

With all good wishes, Simon

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

www.natural-history-conservation.com




> On 6 May 2021, at 22:50, John E Simmons <simmons.johne at gmail.com> wrote:
> 
> Tonya,
> Thank you for your kind words about my book. The recommendation for staging up to 80% concentration was by made by my friend Simon Moore, who I cited in that sentence. In general, I do not recommend using 80% ETOH as a preservative for terrestrial vertebrates, but rather 70%. Preservation is alcohol is a trade-off between dehydration of the specimens and providing them suitable protection against biological deterioration. At 70%, ETOH is a very good biocide; below that, not so good, and above 70%, too strong for most specimens (note that there are some instances in which 80% might be preferred). 
> 
> I do not recommend using stronger alcohol as a hedge against evaporation--that leads to uneven concentrations of preservatives and can be a real mess to work with in a collection.
> 
> For how-to instructions on preserving, transferring specimens, and managing a fluid preserved collection, you might want to check Herpetological Collecting and Collections Management (3rd edition, 2015). The instructions for preserving and managing fluid preserved animals will work for most other specimens as well as for reptiles and amphibians.
> 
> Hope this helps,
> --John
> 
> John E. Simmons
> Writer and Museum Consultant
> Museologica
> and
> Associate Curator of Collections
> Earth and Mineral Science Museum & Art Gallery
> Penn State University
> and
> Investigador Asociado, Departamento de Ornitologia
> Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima
> 
> 
> On Thu, May 6, 2021 at 4:05 PM Haff, Tonya (NCMI, Crace) <Tonya.Haff at csiro.au> wrote:
> Hello all,
> 
> I am enjoying reading John Simmon's fantastic book on fluid preservation. In it I read one suggestion for stepping specimens up out of formalin fixative into preservation alcohol as follows: from 20% ETOH to 40% to 60% and finally to 80%. We typically place our specimens in 70% ETOH, and I know higher concentrations can cause some problems with specimen dehydration. All our specimens are terrestrial vertebrates. I presume the final 80% provides a buffer against ETOH evaporation or leaching of water from the specimen into the fluid in the jar, to ensure that the alcohol concentration in the preservation fluid stays sufficiently high? But to me this is not quite clear. I wonder if any of you have thoughts on this, or if you would be willing to share how you step your specimens up in ETOH? 
> 
> Thank you!
> 
> Tonya
> 
> 
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