[Nhcoll-l] Is there a test to determine what fluid specimens are preserved in -- formalin or ethanol?

Thu Jan 3 06:28:04 EST 2013

To rehydrate or not to.....

Charlie Sturm has pointed out the main caveats and I have always maintained that the decision whether to rehydrate or leave alone is up to the individual, providing they fully understand the pros and cons.
In my experience I have rarely had anything rehydrated that was not worth the effort but these were carefully selected and then they were re-fixed in formalin as a precaution in case any of the stabilising chemical changes brought about by the initial fixation, were undone by the rehydration process; then the hydrated and re-fixed specimens were transferred to a suitable preservative solution - usually 70-80% IMS.  The specimens always look rather brown if they were totally desiccated but look quite fresh if they had not been desiccated for long (months rather than years). 

As Dirk pointed out, if there are more specific issues, then do feel free to ask.

With all good wishes, Simon 

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

  ----- Original Message ----- 
  From: Dirk Neumann 
  To: CSTURMJR at pitt.edu 
  Cc: Cole-Will,Rebecca ; NH Coll ; couteaufin at btinternet.com 
  Sent: Friday, January 04, 2013 7:03 AM
  Subject: Re: [Nhcoll-l] Is there a test to determine what fluid specimens are preserved in -- formalin or ethanol?

  Dear Rebecca,

  completely agree with Charlie. As long as you don't have any climate control issues in your collection that could trigger mould issues, I would leave the dry specimens in the jar as they are. Especially in old historic specimens it is not always clear which type of preservation fluids were used for initial preparation/fixation. There is a whole variety of historic fixatives, some of them include heavy metal salts such as mercury in rather high concentrations (these were often used e.g. for preparations of marine invertebrates). If you don't know the history of preservation/fixation methods in your collection, I would be very careful in handling these specimens. Have in mind that prevailed usage of formaldehyde fixation/preservation starts roughly around 1910. Dried ethanol specimens may look rather poor (not initial fixation, only ethanol preservation = +/- dehydration of specimens to a certain extent). Be careful if your specimens have been prepared prior to 1900 and still look +/- good or show some salty incrustations on the specimens, which could be an indicator for historic fixatives other then formaldehyde.

  Rehydration will not restore the their original shape of specimens. If rehydration is necessary, I would also recommend method Simon Moore suggested in a previous NHCOLL-L posting (see below). For specific questions it might be worth contacting Simon directly.  

  All the best
  Dirk

  *************
  From: Simon Morre, couteaufin at btinternet.com
  Sent: 21/08/2011 12:00:02 GMT Daylight Time
  Subj: Re: [NHCOLL-L:5600] FW: Rehydration of a sea anemone

  Always rather ticklish when you have the holotype to perform such a radical treatment!
  Bear in mind also that rehydration will improve the appearance and texture but it will compromise future DNA extraction/readings.  If you need further advice on this let me know.
  I have also forwarded this to John Simmons who may also have some comments.

  I tend to use Decon-90 at around 3 to 5% in deionised water as a rehydrating agent.
  The reaction is catalysed by warming it to no more than 50 deg. Centigrade (hotplate) and make sure that the container has a loose lid to prevent massive evaporation during warming.
  Obviously photograph and weigh the specimen prior to treatment.
  Start the process first thing as it can take some time and so that you can monitor its progress during the day.  
  The fluid will start to yellow a bit and may smell rather fishy; the specimen will gradually sink into the fluid - this will only happen in an ideal situation, so if the specimen has expanded and feels soft and more flexible like it should if not dry, then it will have reached its 'end-point'.  If it's still floating then it will have air trapped inside.

  In which case.... place the specimen in clean water and place the container inside a vacuum desiccator.  Apply a mild vacuum to it and air should bubble out of the specimen.  After no more than a minute, stop the pump (making sure that the hose is removed from the desiccator and that the tap is closed before the pump is switched off - or it will suck the oil from the pump all over the specimen!!)
  Then release the vacuum slowly and the anemone should sink completely or partly.  Repeat the process until no more air bubbles out.  Small amounts of trapped air will often slowly diffuse out later in the alcohol preservative (see below).
  You should now have a fully rehydrated specimen.  Place into formalin to refix overnight and next day start to transfer into an alcohol dehydration ladder so that by the end of the day, the specimen is preserved in IMS once again.  Ensure that the jar seal is good!  Finally, make a note of the treament for the specimen's record and reweigh the specimen, having drained off excess fluid and re-photo.

  That should hopefully be it!

  With all good wishes, Simon

  Simon Moore MIScT, FLS, ACR,
  Conservator of Natural Sciences,

  Am 04.01.2013 05:34, schrieb CSTURMJR at pitt.edu:

Rebecca,

I will not opine on how to test what solution may have been used to store
the specimens, however, I will question why you might want to rehydrate
them. Unless there is a specific need to rehydrate a specimen, I would
advocate to leave them in a dessicated state. The specimen is already
dessicated and as such will probably stay that way for a long time (unless
something is done to it). Rehydration methods can adversely affect a
specimen. Better methods may be available in the future. Unless there is a
need to rehydrate the specimen for a current study, store it dry. I have
attached a chapter that I wrote six years ago and there are some
references in Section 5.9 that you might like to read before rehydrating.

Hello all,

We have several old collections in the park without any information about
how they were prepared.  Many need to be rehydrated and rehoused into
better storage.  Is there a simple test to determine what they are/were
preserved in before we rehydrate?

thank you

--

Rebecca Cole-Will, Cultural Resources Program Manager  ~  Acadia National
Park, 20 McFarland Hill Drive, PO Box 177, Bar Harbor, ME  04609
 ~207.288.8728 ph., 207.288.8709 fx.
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Regards,
Charlie
.................................................
Charlie Sturm

Treasurer
American Malacological Society

Research Associate - Section of Mollusks
Carnegie Museum of Natural History
Pittsburgh, PA, USA

Associate Professor - Family Medicine
Fellow-American Academy of Family Practice
Fellow-Academy of Wilderness Medicine

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