[NHCOLL-L:5145] RE: white crystals appearing on specimens in fluid, any i...

Fri Dec 17 09:51:40 EST 2010

I agree, Dries.

One reason these can disappear when fluids are changed to alcohol is that  
many triglycerides (unsaturated fats that are mobile and oxidize to fatty  
acids) are alcohol soluble.

Cathy

Catharine  Hawks
Conservator
2419 Barbour Road
Falls Church VA 22043-3026  USA
t/f 703.876-9272
mobile 703.200.4370  

In a message dated 12/17/2010 7:26:23 A.M. Eastern Standard Time,  
A.J.van_Dam at lumc.nl writes:

Dear  Heather,

It is probably the same process that is causing efflorescence  on oil
paintings. There are 3 stages: free fatty acid migration, exudation,  and
crystallization. Although the mechanism is not exactly clear,  the
oxidation and hydrolysis of triglycerides (fats) play a major  role.
Metal ions such as ferro and copper will accelerate the  process.  

Regards,

Dries

Andries J. van Dam,  conservator

Museum of Anatomy
Leiden University Medical Center  
Postal zone T7-P
P.O. Box 9600 
2300 RC Leiden 
The Netherlands  
tel: +31 (0)71 526 9581
fax: +31 (0)71 526 8275 
E-mail:  A.J.van_Dam at lumc.nl
Visiting address: Hippocratespad 21, building  3

Associate scientist, Natural History Museum,  London
http://www.nhm.ac.uk

Directory Board member  ICOM-CC
http://www.icom-cc.org 

Director Alcomon  Company
http://www.alcomon.com 

-----Original  Message-----
From:  owner-nhcoll-l at lists.yale.edu
[mailto:owner-nhcoll-l at lists.yale.edu] On  Behalf Of Heather Campbell
Sent: donderdag 16 december 2010 21:21
To:  NHCOLL-L at lists.yale.edu
Subject: [NHCOLL-L:5137] white crystals appearing  on specimens in fluid,
any ideas?

Hello all,

While  rehousing the bee wet collection I have noticed that some vials
contain  specimens that have white material growing (?) on them.  Here
are
a  few details that may be important when considering a diagnosis:
1. Only  vials containing larvae (maybe pupae) are affected
2. Different species and  different years (but always older than 5yrs)
and
different locals
3.  Preservative used: Kahle's sol
acetic acid (glacial) 10%
formalin (37%)        10%
water     25%
Ethanol  (75%)         55%
4. Easily scraped away and has a  plaque-like resemblance
5. no visible damage done to specimen (naked  eye)

I have pictures but am unable to send due to limits on message  size.  I
will be happy to send these along to anyone who is  interested.

Thank you

Heather M. Campbell
Bee Curatorial  Assistant
Division of Invertebrate Zoology
American Museum of Natural  History
Central Park West @ 79th st.
New York, NY  10024-5192
212-496-3447

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