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<div class="moz-cite-prefix">... it might be worth adding that some
denaturants as some ketones are also used as component in
chromatography and extract pigments quite well (not all, put
some). Natural colours can be caused by quite different effects
and sources, e.g., pigments, unsaturated [metal] ions as key
element in chelating agents, optical refraction on crystals
embedded in tissues, etc..</div>
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<div class="moz-cite-prefix">Often, the effect of visual colour we
see in the specimens we collect is caused by electron excitation
in biomolecules, which cause changes in the bonding or chemistry
of respective molecules. Most of our fixatives and storage fluids
tend to be highly polar, and through polarisation or
depolarisation of respective biomolecules, colours usually fade -
cf. colour reaction in many indicators we use. <br>
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<div class="moz-cite-prefix">There are few natural pigments that are
stable, but admittedly few. And I would always be careful with
bright coloured, historic teaching specimens prepared around 1900
... As old bold bright paints, the ingredient are rarely healthy
(and usually containing heavy metals such as cadmium, chrome,
lead, etc.)<br>
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<div class="moz-cite-prefix">With best wishes</div>
<div class="moz-cite-prefix">Dirk<br>
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<div class="moz-cite-prefix">Am 10.05.2021 um 20:10 schrieb John E
Simmons:<br>
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<blockquote type="cite"
cite="mid:CAF7GCDbrLDSpFEYuRA5Hi1bg5J3oPOppJj=29_ijOokGq84sUw@mail.gmail.com">
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<div class="gmail_default"
style="font-family:tahoma,sans-serif;font-size:small;color:#000000">Gretchen,</div>
<div class="gmail_default"
style="font-family:tahoma,sans-serif;font-size:small;color:#000000">
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><span>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). <span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><span><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><span>A
note in the second edition of <i>The Herbarium Handbook</i>
(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). <span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><span><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><span>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.</span></p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><br>
</p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif">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.</p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><br>
</p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif">Hope
this helps.</p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif"><br>
</p>
<p class="MsoNormal" style="margin:0in 0in
0.0001pt;line-height:normal;font-size:11pt;font-family:"Calibri",sans-serif">--John</p>
<p class="MsoNormal" style="margin:0in 0in
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<p class="MsoNormal" style="margin:0in 0in
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data-smartmail="gmail_signature">
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<div dir="ltr"><font
size="2"><span
style="font-family:tahoma,sans-serif">John
E. Simmons<br>
Writer and Museum
Consultant</span></font></div>
<div dir="ltr"><font
size="2"><span
style="font-family:tahoma,sans-serif">Museologica<br>
<i>and</i><br>
Associate Curator
of Collections<br>
Earth and Mineral
Science Museum
& Art Gallery<br>
Penn State
University<br>
<i>and</i><br>
Investigador
Asociado,
Departamento de
Ornitologia<br>
Museo de Historia
Natural,
Universidad
Nacional Mayor de
San Marcos, Lima</span></font><br>
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<div dir="ltr" class="gmail_attr">On Fri, May 7, 2021 at 4:37 PM
Gretchen Meier <<a href="mailto:gameier@d.umn.edu"
moz-do-not-send="true">gameier@d.umn.edu</a>> wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi there!
<div>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?<br>
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-- <br>
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<div dir="ltr">Gretchen Meier (<i>she/her/hers</i>)</div>
<div dir="ltr">
<div>Olga Lakela Herbarium (DUL)</div>
<div>University of Minnesota
Duluth</div>
<div><a
href="mailto:gameier@d.umn.edu"
target="_blank"
moz-do-not-send="true">gameier@d.umn.edu</a></div>
<div>218.726.6542</div>
<div><br>
</div>
<div><i>Naturum expellas furca,
tamen usque recurret - Homer </i></div>
<div>'you may drive nature out
with a pitchfork, but she will
come hurrying back'</div>
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