[Nhcoll-l] [EXTERN] Removing specimens from formaldehyde

[John E Simmons]

Vanessa,
Dirk's advice is correct.

The reason we lack reliable recommendations for soaking time for each step
is that there are too many variables to consider, such as the
surface-to-volume ratio of the specimen, thickess of the specimen, whether
the specimen has thin skin, scales, fur, a shell, and so forth, and the
density and structure of the dermal layers and internal tissues.

There are several papers that give penetration times for formaldehyde or
ethanol, but these rates should not be extrapolated for whole specimens.
All of the published penetration rates   that I have reviewed  are based on
small samples (often no more than 1 cubic cm in volume) of gels or agars,
etc., so the penetration rates are not transferable to whole organisms. For
example, the penetration rates of formaldehyde published by Steedman (1976)
are based on gelatin and casein gels, Medawar (1941) used plasma clots, and
Baker (1958) used gelatin/albumin gels.

The rate of penetration of fixatives and preservatives is complicated by
the fact that the chemicals modify the tissues as they penetrate them,
which greatly impedes the rate of penetration of more of the fluid, and
quickly limits the depth of penetration of the fluid (this is why it is
recommended to inject formaldehyde or other fixatives into specimens). In
addition, penetration rates of preservative fluids are temperature
dependent.

I hope that someday we will have enough research on penetration, fixation,
and preservation rates that we can come up with some general guidelines for
time required for each soaking step, but until that day comes, Dirk's
advice is the best we have.

--John

John E. Simmons
Writer and Museum Consultant
Museologica
*and*
Investigador Asociado, Departamento de Ornitologia
Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima


On Mon, Sep 30, 2024 at 11:30 AM Dirk Neumann <d.neumann at leibniz-lib.de>
wrote:

> Dear Vanessa,
>
> rising and staging times depends on the size of the specimens and how
> readily superfluous the formaldehydes is diluted from them. The specimens
> shown may require 2-3 days of rinsing, and then slowly going up
> 20/40/60/70. Each of these steps may take 1 week or longer, it depends how
> much formaldehyde comes out of them.
>
> All together you should assume at least a month, but it can take you
> longer.
>
> With all best wishes
> Dirk
>
>
> Am 30.09.2024 um 17:14 schrieb Vanessa Pitusi:
>
> Dear all,
>
>
>
> Recently, I have discovered that most of our larger specimens kept in the
> large collection jars, are kept in formalin (photo for reference).
>
>
>
> I have looked into removing the specimens from formalin and placing them
> into ethanol. I understand the steps that have to be taken, but I was
> wondering if anyone has advice on the soaking time for each step. That is
> the only thing that is kept vague in the texts that I have read. One
> reference mentioned that tortoises and racoons take two to three days.
>
>
>
> Most the specimens that I will work with a large fish, cephlapods, and
> birds.
>
>
>
> In case any of you have done this, any advice on this or the process is
> appreciated!
>
>
>
> I am also open to having a quick chat via Teams or Zoom.
>
>
>
> Kind regards,
>
> Vanessa
>
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> --
>
> ******
>
>
>
> *Dirk Neumann*
>
> Collection Manager, Hamburg
>
>
>
> Postal address:
>
> *Museum of Nature Hamburg*
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>
> of Biodiversity Change
>
> Dirk Neumann
>
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>
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>
> *d.neumann at leibniz-lib.de <d.neumann at leibniz-lib.de>*
>
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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)
> Sitz der Stiftung: Adenauerallee 160 in Bonn
> Vorsitzender des Stiftungsrates: Dr. Michael Wappelhorst
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> Natural History Collections (SPNHC), an international society whose
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> 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.
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