[Nhcoll-l] Borax as a buffer for ethanol-preserved zoological specimens

[Simon Moore]

Just to add to John’s list - hopefully you are not diluting your ethanol with tap water as the ethanol will precipitate salts in the tapwater into an undesirable deposit. 

With all good wishes, Simon 

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

www.natural-history-conservation.com



> On 7 May 2026, at 18:06, John E Simmons <simmons.johne at gmail.com> wrote:
> 
> Before responding to your interesting question, we need a little more information.
> 
> Why do you think your 75% ETOH might become acidic over time? The presence of the molluscan specimens alone provides a base (calcium) to buffer it. What is the source of acidification that you think you may have?
> 
> What is the pH of the water you use to dilute your ETOH to 75%? Are you using tap water? Deionized water? Distilled?
> 
> Borax is not a stable buffer over time--it works well initially, but over time may itself service as a source of acidification. I presume the molluscan specimens in fluid include tissues other than shells, in which case a preservative that is too basic will probably damage the proteinaceous parts of the specimen.
> 
> How are the specimens treated before they are put into 75% ETOH? Do you use a fixative? If so, what is it?
> 
> --John
> 
> John E. Simmons
> US Fulbright Senior Scholar
> Writer and Museum Consultant, Museologica
> and
> Research Associate, Earth and Mineral Sciences Museum & Art Gallery, Penn State University
> and
> Investigador Asociado, Departamento de Ornitología, Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima
> 
> 
> On Thu, May 7, 2026 at 9:48 AM Katharina von Oheimb <katharina.von.oheimb at gmx.de> wrote:
> 
> Hi everyone,
>  
> At the Museum für Naturkunde Berlin, we use 75% denatured ethanol as the standard preservative for fluid-preserved molluscan specimens. We are currently evaluating the addition of borax (sodium tetraborate) as a buffering agent, as it is practised in some other museum collections of molluscs. The rationale is that unbuffered ethanol might become acidic over time, potentially damaging the carbonate shells of molluscan specimens, in particular the very thin and minute ones. I can imagine that this issue is also relevant for ethanol-preserved samples of other animal groups with calcium carbonate structures.
>  
> I would be very interested to hear about your experiences with borax-buffered ethanol for the long-term preservation of zoological specimens. In particular, I would like to know:
>  
> - What recipe do you use for mixing it?
> - Have you observed any effects on DNA quality?
> - Have you encountered any other undesirable effects, such as deposits on specimens or other changes in specimen condition?
>  
> Looking forward to hear from you!
>  
> Katharina von Oheimb
> **************************************
> Dr. Katharina von Oheimb
> Museum für Naturkunde
> Leibniz Institute for Evolution and Biodiversity Science
> Invalidenstraße 43
> 10115 Berlin
> Germany
> 
> E-mail: katharina.von.oheimb at gmx.de
> Website: https://www.museumfuernaturkunde.berlin/en/the-museum/about-us/team/details/katharina-c-m-von-oheimb/
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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.