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

Mon Sep 30 16:24:18 EDT 2024

There are several drawbacks to using the suggested steps of 30-50-75.

According to Waller and Strang (1996), transfer in concentration steps
greater than 20% risks causing cellular rupture to specimens because of the
effect of ethanol concentration on osmotic pressure (see figure 7 in Waller
and Strang). As stated in their paper, “…it is clear that the osmotic
pressure rises steadily with ethanol concentrations for solutions below
about 75% v/v and begins to rise more rapidly at concentrations above about
80% v/v. These facts suggest that, from considerations of osmotic pressure,
solutions with approximately equal concentrations are appropriate for
stepping specimens up to higher ethanol concentrations, up to about
75%v/v.” This means that the abrupt change from water to 30% ETOH should be
avoided, and as the concentration of ethanol nears 75% it is very close to
the osmotic pressure shift, which should also be avoided by not going above
70%.

In addition, starting with the abrupt change to 30% ETOH will cause more
rapid dehydration than a 20% step, and rapid dehydration is potentially
destructive to tissues.

Lastly, the assumption that using 75% ethanol may result in a 70%
concentration after stepping up may well be incorrect (depending on the
volume of fluid used and the specimen). The recommendation for using 70%
ethanol is based on the fact that 70%, ETOH is a very good biocide, but
ethanol preservation is balance between providing an antiseptic environment
and excessive dehydration of the specimens, so there is no reason, but some
risk, in using ETOH at concentrations greater than 70% (see figures 12 and
13 in Waller and Strang 1996).

Referernce:

Waller and Strang. 1996. Physical chemical properties of preservative
solutions—I. Ethanol-water solutions. *Collection Forum* 13(2):70-85

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 3:53 PM Dirk Neumann <d.neumann at leibniz-lib.de>
wrote:

> Hi Dries and all,
>
> also added offline that especially with these large specimens it would be
> worth keeping an eye on layering. The final concentration should be at 70%,
> and you are correct that it might be worth filling the jar up with 75%
> instead of 70% to end up at 70% (and not 65%).
>
> But I am not sure that the steep steps 30/50/70 are necessary for
> achieving this; if specimens have been sitting in formalin for long time,
> it might be worth considering lees steep steps (0/20/40/60/70-75) and allow
> for more time.
>
> Pragmatically, when I had to handle a lot of large specimens (often large
> whitefish), there was the risk of what where cautioning, i.e. that
> specimens would arrive too fast at "70%" and the residual water could
> dilute the ethanol concentration to well below 70%.
>
> Therefore, I delayed labelling of specimens usually for some time and
> "added" the time it took to rearrange shelves to free space to monitor the
> freshly filled 70% jars if I could spot any layering. You could also
> exchange the 70% after half a year to make sure that the concentration has
> not dropped significantly below 70%.
>
> Both concentrations surely work, but I always preferred the slower option.
>
> All the best
> Dirk
>
>
> Am 30.09.2024 um 20:28 schrieb a.j.van_dam at lumc.nl:
>
> Dear Vanessa,
>
> There is a very simple way to monitor the progress of fluid exchange when
> transferring specimens from an aqueous solution of 4% formaldehyde to 70%
> ethanol.
>
> Since the density of ethanol (d=0.79) is much lower than the density of
> water (d=1.00) and the density of buffered formaldehyde 4% (d=1.02), during
> the time the specimen is in one of the transfer baths (ethanol
> 20-40-60-70), the density of the surrounding fluid will slowly rise due its
> exchange with the heavier fluid inside the specimen.
>
> When measuring the surrounding fluid periodically (e.g. once a week) with
> a densimeter you will see a logarithmic decrease in density until there is
> hardly a significant change anymore, which indicates that the transfer step
> has been fully completed and the specimen can be placed in the next bath.
> This way of monitoring will ensure correct transfer times without having to
> worry about the variables of type of specimen, shape, size, etc.
>
> Like Dirk and John, I would also recommend four baths, but with slightly
> different concentrations: 30-50-70-75, which gives after complete exchange
> an end concentration a little over 70%.
>
> Kind regards,
>
> Dries
>
> *Andries J. van Dam
> <https://www.linkedin.com/profile/preview?vpa=pub&locale=en_US>* |
> curator-conservator
>
> *Anatomical Museum
> <https://www.lumc.nl/onderwijs/over-ons/anatomisch-museum/?setlanguage=English&setcountry=en>* |
> Directorate of education | Leiden University Medical Center | Building 3
> (V3-32)
> P.O.Box 9600 | 2300 RC Leiden | Netherlands
> Visiting address: Hippocratespad 21 | Tel: +31 (0)71 52 68356 | E-mail: *A.J.van_Dam at lumc.nl
> <A.J.van_Dam at lumc.nl>*
>
> Scientific associate | Natural History Museum London
>
> ------------------------------
> *Van:* Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu>
> <nhcoll-l-bounces at mailman.yale.edu> namens John E Simmons
> <simmons.johne at gmail.com> <simmons.johne at gmail.com>
> *Verzonden:* maandag 30 september 2024 17:55
> *Aan:* Dirk Neumann <d.neumann at leibniz-lib.de> <d.neumann at leibniz-lib.de>
> *CC:* nhcoll-l at mailman.yale.edu <nhcoll-l at mailman.yale.edu>
> <nhcoll-l at mailman.yale.edu>
> *Onderwerp:* Re: [Nhcoll-l] [EXTERN] Removing specimens from formaldehyde
>
> 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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> --
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> ******
>
>
>
> *Dirk Neumann*
>
> Collection Manager, Hamburg
>
>
>
> Postal address:
>
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>
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>
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>
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>
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>
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>
> Stiftung des öffentlichen Rechts;
> Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian
> Grüter (Kaufm. Geschäftsführer)
> Sitz der Stiftung: Adenauerallee 160 in Bonn
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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.
>
>
> --
>
> ******
>
>
>
> *Dirk Neumann*
>
> Collection Manager, Hamburg
>
>
>
> Postal address:
>
> *Museum of Nature Hamburg*
> Leibniz Institute for the Analysis
>
> of Biodiversity Change
>
> Dirk Neumann
>
> Martin-Luther-King-Platz 3
>
> 20146 Hamburg
> +49 40 238 317 – 628
>
> *d.neumann at leibniz-lib.de <d.neumann at leibniz-lib.de>*
>
> www.leibniz-lib.de
>
>
>
> --
> 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
>
>
> --
> 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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