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

[Simon Moore]

Hi Sarah,

Glycerin can be used as an effective preservative for transparency specimens in that its specific gravity is physically supportive of these specimens which have been through a maceration process to render the internal skeleton more visible plus its RI lends itself to rendering the specimens even more transparent.  It often used to be used in mircoscopy for a similar reason.  The more concentrated the glycerin, the more support it will give.
It can be mixed with alcohol but bear in mind the two form a binary azeotrope whose mixing will release tiny air bubbles and which need to dipserse before the solution can be used.  You will also see much in the way of Schleren Optics whilst the two fluids are mixing, once these and the air bubbles are gone, then the fluid may be used.
Glycerin, as most other viscous fluids, is also capable of 'escaping' from jars - how many times have sticky rings appeared under such a container?
Thymol is useful to prevent mould growth but a small crystal of menthol does just as well, imparting a fine film barrier across the surface of the fluid and it has a more pleasant and less permeating odour than thymol. 
For storage, you may use either ethanol (70%) as a preservative but bear in mind a huge osmotic pressure differential between the fluids so such a transfer would have to be done gradually and in stages; the specimens would lose their alcohol-induced opacity.  Also bear in mind the problems involved with alcohol flammability, evaporation leading to auto-dilution.  I would personally prefer to use the glycerin but make sure that you have good containers/jars with a tight and glycerin-proof seal!

I hope that these comments will help.

With all good wishes, Simon. 

Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian,
www.natural-history-conservation.com 


  ----- Original Message ----- 
  From: Sarah K. Huber 
  To: nhcoll-l at mailman.yale.edu 
  Sent: Tuesday, August 19, 2014 4:53 PM
  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 | www.vims.edu
  PO Box 1346 | Rt. 1208 Greate Rd., Gloucester Pt., VA 23062

   



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