[Nhcoll-l] Long-term Storage of Cleared and Stained Specimens

Thu Aug 21 05:15:32 EDT 2014

Sarah and all,

Glycerin is a very effective and stable preservative (>60%). It is used for more than a century in pathological collections, because it enables also the preservation of (blood) colour. It's mechanism of action seems similar to ethanol. In high concentrations it is a denaturant by protein coagulation and precipitation an thus even has (pseudo-)fixative properties although its penetration rate is very low. The German Kaiserling (1896) was one of the first who described a method to preserve anatomical preparations in natural colours by using a glycerine based preservative.

Note that adding a mold growth inhibitor (like thymol; suspected of being a carcinogen and considered to be moderately toxic) is only necessary when you are not able to prevent high humidities (>55%) in your storage facility. When the RH is complying to the standard guidelines for storing fluid preserved specimens (RH between 35-55%) molds simply cannot grow on/in high concentrations of glycerine (>60%).

Regards,

Dries
Andries J. van Dam, conservator

Museum of Anatomy
Leiden University Medical Center
Building 3 (V3-32)
P.O.Box 9600
2300 RC Leiden
The Netherlands
tel: +31 (0)71 52 68356
E-mail: A.J.van_Dam at lumc.nl<mailto:A.J.van_Dam at lumc.nl>
Visiting address: Hippocratespad 21
Scientific associate Natural History Museum London
http://www.nhm.ac.uk<http://www.nhm.ac.uk/>
Directory Board member ICOM-CC
http://www.icom-cc.org<http://www.icom-cc.org/>

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

From: nhcoll-l-bounces at mailman.yale.edu [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Bentley, Andrew Charles
Sent: woensdag 20 augustus 2014 16:28
To: Sarah K. Huber; nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] Long-term Storage of Cleared and Stained Specimens

Sarah

It is my understanding that the major reasons for keeping C&S materials in glycerin are support (now that all muscle has been removed from the specimen it is more susceptible to bending, damage etc.) and clarity (glycerin has a specific refractive index that makes these specimens highly visible).  As Glycerin is a vegetable based product and not a preservative or fixative, the thymol is necessary to prevent mold growth on specimens (one of two crystals is usually enough).  Given the difference in specific gravity of glycerin and ethanol I would be concerned about changes in the specimen brought about by a change to 70% ethanol.  That being said, theoretically all that is left is bone and cartilage (and some connective tissue) which should be less susceptible to shrinkage in the first place.  I do know that some researchers like to "cut" their glycerin with a little ethanol (10-20%) to make it a little less viscous and easier to work with but that would have little effect on the specimens.  As for specimens that were transferred some time back, I wouldn't think it would be too harmful to get them back into glycerin as long as this process was staged through increasing concentrations of glycerin:alcohol.

Andy

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Andy Bentley
Ichthyology Collection Manager
University of Kansas
Biodiversity Institute
Dyche Hall
1345 Jayhawk Boulevard
Lawrence, KS, 66045-7561
USA

Tel: (785) 864-3863
Fax: (785) 864-5335
Email: abentley at ku.edu<mailto:abentley at ku.edu>
http://ichthyology.biodiversity.ku.edu<http://ichthyology.biodiversity.ku.edu/>

SPNHC President
http://www.spnhc.org<http://www.spnhc.org/>

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From: nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu> [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Sarah K. Huber
Sent: Tuesday, August 19, 2014 10:53 AM
To: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: [Nhcoll-l] Long-term Storage of Cleared and Stained Specimens

I am curious to hear what people think is the best long-term storage medium for cleared and stained specimens (in our case fishes). I have seen recommendations for glycerin in concentrations ranging from 100-70%, and dilutions with water, ethanol, or KOH. I have also seen arguments for and against the addition of thymol. However, since our collection has had mold outbreaks in the past, any long term storage medium we use must have some kind of additive to prevent molding.

In addition, I have come across some older cleared and stained specimens that were transferred to 70% ethanol at some point in the distant past. Is it recommended to keep these specimens in ethanol or to try and move them back into glycerin?

Thanks in advance,

Sarah

Sarah K. Huber, Ph.D.
Research Assistant Professor of Biology and Marine Science
Collection Manager, VIMS Ichthyology Collection
804.684.7104 | Collection 804.684.7285
skhuber at vims.edu<mailto:skhuber at vims.edu> | www.vims.edu<http://www.vims.edu>
PO Box 1346 | Rt. 1208 Greate Rd., Gloucester Pt., VA 23062

[Image removed by sender. VimsLogo]
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