[NHCOLL-L:5143] RE: white crystals appearing on specimens in fluid, any i...

Fri Dec 17 04:51:19 EST 2010

Dear Dirk, Heather and Kate,

Many thanks for this extra information.  p-formaldehyde crystals can  be 
prevented by the addition of 2% (I think!) methanol to your formalin  stock.  
Encrusted specimens can be rescued by immersing them in  preservative 
strength alcohol, and although it takes a few days, the crystals do  gradually 
melt away into solution.  This also applies to dried out  specimens.  After a 
water rinse they can then be rehydrated as  normal.

With all good  wishes, Simon

Simon Moore MIScT, FLS, ACR,
Conservator of Natural  Sciences,
20 Newbury Street,
Whitchurch RG28 7DN.
_www.natural-history-conservation.com_ 
(http://www.natural-history-conservation.com/)  
_www.pocket-fruit-knives.info_ (http://www.pocket-fruit-knives.info/)  

_http://uk.linkedin.com/in/naturalsciencespecimenconserve_ 
(http://uk.linkedin.com/in/naturalsciencespecimenconserve)   

In a message dated 17/12/2010 08:13:33 GMT Standard Time,  
Dirk.Neumann at zsm.mwn.de writes:

Hello  Heather, 

I have observed similar encrustations on fish specimens. It  seems that 
this is especially a problem of species with a fat rich diet (or  fatty 
specimens in general), e.g. in phytophagus Tilapias or in cyprinids.  Those 
incrustations, which might also grow on included labels or forms a  flocculent  
precipitation on the bottom of the lot, may be easily removed  when rinsing the 
specimen with hand warm/hot water. Changing the preservative  fluid and 
cleaning the container would be advisable.

Crystalline,  paraformaldehyde encrustations are more difficult to remove, 
as they  (normally) appear (at least in fishes) within or underneath of bony 
 structures, e.g. within the lateral line canal or below scales. Unlike  
cholesterol (Thanks for this hint, Simon & Judith!), these crystals  
apparently destroy the bony structures and removing is more difficult. I had  some 
good results with placing such specimens for some 10-15 min in hand warm  
water, adding little bit detergent, and then carefully brushing the  
precipitation off  with a soft bottle brush. This has to be done very  carefully and 
always into the direction e.g of scales (never against!), as  infected scales 
or other bony structures tend to be very weak and can be  damaged easily.

A possible reason for this paraformaldehyde crystals  might be usage of 
unbuffered formaldehyde solution for fixation - at least I  recognised this 
kind of problem quite frequently with specimens, which have  been preserved 
with formaldehyde obtained somewhere in an African pharmacy. A  second issue 
here might be inadequate production based on paraformalin  solution. 
Tentatively, this seems to be a problem again with more fatty  specimens/species, and 
I would not be surprised if shifts of the pH to values  below 7 caused by 
dissolved fatty acids from the specimens would speed up this  process. Before 
crystal manifestations on the specimens starts to grow, you  should be able 
to recognise a very fine paraformaldehyde precipitation, either  as needles 
or floating in the fluid. If that occurs, changing of the alcohol  and 
rinsing of specimens with alcohol would be strongly  recommended.

Hope this helps,

All the  best
Dirk

Am 16.12.2010 23:47, schrieb _Couteaufin at aol.com:_ 
(mailto:Couteaufin at aol.com:)   
Heather,

I have observed this before on specimens prepared by Fric (Prague) et  al. 
where little white waxy blobs form on the edge of the vials covered with  
netting - I presume that yours are similar.
Chemically these should dissolve in alcohol but if the preservative  
contains enough aqueous-based reagents then the precipitation/coagulation is  
possible.  Could well be cholesterol.  I am still surprised  however, that it 
forms on top of the tubes rather than the specimens  themselves.

Hope that this ramble is useful in some way.

With all  good wishes, Simon

Simon Moore MIScT, FLS, ACR,
Conservator of  Natural Sciences,
20 Newbury Street,
Whitchurch RG28 7DN.
_www.natural-history-conservation.com_ 
(http://www.natural-history-conservation.com/)  
_www.pocket-fruit-knives.info_ (http://www.pocket-fruit-knives.info/)  

_http://uk.linkedin.com/in/naturalsciencespecimenconserve_ 
(http://uk.linkedin.com/in/naturalsciencespecimenconserve)   

In a message dated 16/12/2010 22:20:54 GMT Standard Time, 
_JPRICE at mus-nature.ca_ (mailto:JPRICE at mus-nature.ca)  writes:

Heather

I had similar stuff in a jar of tapeworms,  although in this case it was 
white pearly flakes. I had our mineralogy  guys run it under the x-ray 
chromatograph.  They tell me it's  cholesterol, likely dissolved out of the tissues 
and then  precipitated.

But dammit Jim, I'm a collection manager, not a  chemist!
Judith

Judith C. Price
Secretary, Society for the  Preservation of Natural History Collections
Assistant Collections  Manager, Invertebrates / Gestionnaire adjointe des 
collections  invertébrés
Canadian Museum of Nature / Musée canadien de la  Nature
PO Box 3443 Station D / CP 3443 Succ  <<D>>
Ottawa, Ontario K1P  6P4 CANADA
Tel.613.566.4263 / Fax.613.364.4027
_jprice at mus-nature.ca_ (mailto:jprice at mus-nature.ca) 
@nature_jcp
_www.nature.ca_ (http://www.nature.ca/)  / _www.spnhc.org_ 
(http://www.spnhc.org/) 

-----Original  Message-----
From: _owner-nhcoll-l at lists.yale.edu_ 
(mailto:owner-nhcoll-l at lists.yale.edu)   [_mailto:owner-nhcoll-l at lists.yale.edu_ 
(mailto:owner-nhcoll-l at lists.yale.edu) ]  On Behalf Of Heather Campbell
Sent: Thursday, December 16, 2010 3:21  PM
To: _NHCOLL-L at lists.yale.edu_ (mailto: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

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

-- 

Dirk Neumann

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email: Dirk.Neumann(a)zsm.mwn.de

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