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

[John E Simmons]

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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