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

Thu May 7 15:54:34 EDT 2026

Have any of the people who responded to your query mentioned what pH they
started with or ended up with? Assuming that a solution is or may become
acidic and adding a buffer, particularly one as unreliable as borax, is not
a good practice. The fact that no one has noticed harm with it does not
mean that it is not having unwanted effects.

Most of the literature on buffering in fluid preservation is about
buffering formaldehyde, which is far more acidic than one would expect
alcohol to become if, in fact, fluids from the specimens cause it to become
acidic. It is quite possible that over-buffering will have more negative
effects on specimens than slightly acidic alcohol (if, in fact, it really
acidifies from the extraction of body fluids). What usually drives the
acidification of alcohol-based preservatives is the deterioration of
extracted lipids. Simon can comment more on this subject.

Before you proceed with buffering with borax, you might want to check the
following:

Hughes, G. W., and J. A Cosgrove. 1990. pH change in a formalin borax
solution with inferences about uses of neutralized formalin in vertebrate
collections. *Collection Forum* 6(1): 21-6.

Motoda et al. (1976) found that borax, trioxane, magnesium chloride, and
hexamine buffers in formaldehyde all caused clearing of marine zooplankton
and that pigments faded with hexamine (the authors recommended the use of
formaldehyde and seawater without any additional buffering agents due to
the salt content of the seawater). The reference is:

Motoda, S., R. Marumo, and T. Tokioka. 1976. Fixation and preservation
experiments on marine zooplankton in Japan: Outline of experiments and
results. Pages 325-332 in Steedman, H. F.

(editor). *Zooplankton Fixation and PreseNation. *Monographs on
Oceanographic Methodology 4. The UNESCO Press, Paris, 350 pages.

Aso in the same volume as the Motoda paper, Steedman reported that the use
of a borax buffer with paraformaldehyde produces a solution with a pH of
8.2:
Steedman, H. F. 1976b. General and applied data on formaldehyde fixation
and preservation of marine zooplankton. Pages 103-154 in Steedman, H. F.
(editor). Zooplankton Rxation and Preservation. Monographs on Oceanographic
Methodology 4. The UNESCO Press, Paris, 350 pages.

Taylor, W.R. 1977. Observations on specimen fixation. Proceedings of the
Biological Society of Washington 90(4): 753-63.

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 3:31 PM Katharina von Oheimb <
katharina.von.oheimb at gmx.de> wrote:

> Thanks for getting back to me, John and Simon. We always use deionized
> water for diluting the ethanol. A fixative is not used for our specimens.
> Collected terrestrial gastropods are usually drowned in water with menthol
> crystals for relaxation, and then directly transferred into ethanol, which
> is subsequently changed a few times.
>
> My main concerns regarding potential shell damages refer to specimens that
> are either thin-shelled, in particular semi-slugs with comparatively large
> bodies, or very small, where jars contain a larger volume of ethanol
> compared to the shells.
>
> Information on ethanol getting acidic over time is for example given in
> the book “The Mollusks - A Guide to Their Study, Collection, and
> Preservation” edited by Sturm et al. (2006). (See here for a pdf version:
> https://www.researchgate.net/profile/Angel_Valdes5/publication/278368256_The_Mollusks_A_Guide_to_Their_Study_Collection_and_Preservation/links/58723ce808aebf17d3af55b7/The-Mollusks-A-Guide-to-Their-Study-Collection-and-Preservation.pdf
> )
>
> Quote from a chapter by Pearce (p. 194): “For long-term storage,
> preservatives should be chemically buffered to prevent the shell from
> dissolving. Preservatives can become acidic from natural fluids leaching
> out of the soft tissues. The acidity can dissolve the calcium carbonate
> from the shells. A number of buffers exist to control pH. An inexpensive
> buffer used at the Delaware Museum of Natural History is a saturated
> solution of borax (sodium borate) in the ethanol (less than one gram per
> liter).”
>
> Quote from a chapter by Pearce and Örstan (p. 279): „Use at least five
> volumes of alcohol for each volume of body tissue to avoid too much
> dilution of preservative by body fluids. For long term storage in liquids
> (several months or more) be sure to buffer the solution against acidity so
> the shells do not dissolve. One substance that is commonly used as a buffer
> is sodium borate (Borax). Adding a teaspoon (10 g) to a liter of ethanol
> will provide an adequate buffering capacity.”
>
> I raised this issue also in the Mollusca-list and got this response from
> John Hutchinson from the Senckenberg Museum of Natural History Görlitz:
>
> “In Görlitz we have been routinely adding borax to our alcohol for many
> (20+) years. Our motivation was to prevent shell dissolution by the slighly
> acidic ethanol solution. More recently I have heard that acidity promotes
> DNA breakage, so the borax might help in this respect too. Certainly we
> have no particular problems in DNA sequencing our material by standard
> methods, and experience leads us to suspect that the DNA has remained in
> better condition for longer than in many other collections; but this really
> needs a properly controlled experiment to examine. Sure, there are better
> ways to be sure of preserving DNA, but for us it is important to leave the
> animals suitable for dissection.
> We add a "pinch" (i.e the tip of teaspoon) of powdered borax to our 4 L
> casks of 75% solution of denatured ethanol. This little amount is enough to
> form a saturated solution, with a few grains remaining undissolved at the
> bottom of the cask. We have not noticed any deposits on shells, but most of
> our collection is slugs.”
>
> Best wishes,
>
> Katharina
> --------------
> *Gesendet: *Donnerstag, 7. Mai 2026 um 19:46
> *Von: *"Simon Moore" <couteaufin at btinternet.com>
> *An: *"John Simmons" <simmons.johne at gmail.com>
> *CC: *"Katharina von Oheimb" <katharina.von.oheimb at gmx.de>,NHCOLL-new <
> nhcoll-l at mailman.yale.edu>
> *Betreff: *Re: [Nhcoll-l] Borax as a buffer for ethanol-preserved
> zoological specimens
> 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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