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

Thu May 7 15:57:08 EDT 2026

Chiming in; if you dilute the Ethanol yourself, use tab water; if I remember correctly, the Berlin tab water i´slightly chlorinated, you need to put a air bubbler in to drive the chlorine out. The Berlin tab water is slightly calciferous, that should do as a buffer for the pH. Do not use distilled water, because distilled water attracts carbon dioxide and builds up a bicarbonate buffer system which leans strongly to pH4.

There is the very nice work of Marion Kotrba on the pH in Ethanol; her assessment showed nicely, that low pH concnetrations in crustaceans is not that much of an issue (the pH tends rather to be between 7-8.

https://collection-forum.kglmeridian.com/view/journals/cofo/31/1-2/article-p84.xml

Hope this helps
Dirk

Am 07.05.2026 um 19:06 schrieb 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<mailto: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
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Stiftung Leibniz-Institut zur Analyse des Biodiversitätswandels
Postanschrift: Adenauerallee 127, 53113 Bonn, Germany

Stiftung des öffentlichen Rechts;
Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Grüter (Kaufm. Geschäftsführer)
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