[Nhcoll-l] Alcohol concentration for terrestrial vertebrates

Fri May 7 02:35:33 EDT 2021

Hi Tonya (and John and Simon ;-)

concur with John and Simon, specimens should be kept in 70%; Simon 
pointed to the diluting effects and the image below nicely illustrates 
this: even if you use more steps for transferring specimens 
(0/20/40/60/80 vs. 20/30/50/70), tissues are still soaked with 60% or 
less high concentrated EtOH.

Depending on size, body mass and number of specimens (i.e. amount of 
tissue in the jar), the effect can be considerable (see "staining" in 
the images below; in the left one, body fluids released from these tall 
whitefish are indicated by the reddish haemoglobin stain at the bottom 
of the jar, the overall greenish colour in the right comes from 
chlorophyll released from the guts of these herbivorous distichodus fish).

I do the initial filling usually with 73-75% EtOH to reach 70%; aside 
from vertebrates high EtOH concentrations can be an issue in malaise 
traps because there the specimens usually are collected over several 
days or weeks in 96-80% EtOH. As Simon pointed out this quickly 
dehydrates specimens and weakens the joints holding all the antennae, 
appendices, bristles of invertebrates. Another issue is that in unsorted 
malaise trap samples there often is a thick deposit of specimens at the 
bottom of the container. Because the diluted less high concentrated 
ethanol is heavier, it layers at the bottom of the jar (cf. whitefish 
jar). Inside malaise trap containers, this diluted EtOH may get trapped 
in the thick specimen deposit.

Usually, I leave jars for few day to see if there are any unwanted 
effects before moving them into the collection.

Hope this is useful, with best wishes
Dirk

Am 07.05.2021 um 00:17 schrieb 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 
> <http://www.natural-history-conservation.com>
>
>
>
>
>> On 6 May 2021, at 22:50, John E Simmons <simmons.johne at gmail.com 
>> <mailto: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 <mailto: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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-- 

Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
neumann(a)snsb.de

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---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
neumann(a)snsb.de

postal address:

Bavarian Natural History Collections
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