[Nhcoll-l] Alcohol concentrations for preserving flowers

[John E Simmons]

Gretchen,

I was hoping that a botanist might respond on the list with a
recommendation for you (botany is not my specialty). I can tell you that
the original Kew mixture was 53 percent industrial methylated spirits (IMS,
which is ethyl alcohol containing 9 percent water and 2–4 percent
methanol), 37 percent water, 5 percent formalin (“dilute formaldehyde”),
and 5 percent glycerol (Forman and Bridson 1989).



A note in the second edition of *The Herbarium Handbook* (1992) stated that
due to controls on hazardous chemicals, the original formula at Kew had
been withdrawn and replaced by a mixture of “70% alcohol (ethanol, or
ethanol + trace of methanol), 29% water and 1% glycerol. If using 90%
strength Industrial Methylated Spirit (IMS) the mixture is 78% IMS, 21%
water and 1% glycerol. With different strengths of IMS the proportions must
be adjusted accordingly” (Forman and Bridson 1989, 210).



In the third edition (Bridson and Forman 1998) the Kew mixture recipe was
ten parts IMS, one part formalin, one part glycerol, and eight parts water.


The Kew mixture was supposed to help preserve the color in plants. If your
concern is just to preserve flowers sufficiently for them to be dissected,
you might try 70% ETOH, with no other additions. If the specimens are not
intended to be saved as museum specimens, you could use denatured 70% ETOH,
which is considerably less expensive.


Hope this helps.


--John


John E. Simmons
Writer and Museum Consultant
Museologica
*and*
Associate Curator of Collections
Earth and Mineral Science Museum & Art Gallery
Penn State University
*and*
Investigador Asociado, Departamento de Ornitologia
Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima


On Fri, May 7, 2021 at 4:37 PM Gretchen Meier <gameier at d.umn.edu> wrote:

> Hi there!
> Is there a recommended ETOH concentration for preserving flowers for later
> dissection? In a pinch, I've used cheap vodka (about 40%) but I'm not sure
> I want to bring that into a classroom.  Any suggestions?
>
> --
> Gretchen Meier (*she/her/hers*)
> Olga Lakela Herbarium (DUL)
> University of Minnesota Duluth
> gameier at d.umn.edu
> 218.726.6542
>
> *Naturum expellas furca, tamen usque recurret - Homer *
> 'you may drive nature out with a pitchfork, but she will come hurrying
> back'
>
>
>
>
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