[Nhcoll-l] fluid specimens and iodine staining

[Milensky, Christopher]

Hello,
I am hoping that some folks in the NHCOLL community have experience with iodine staining and would be willing to share their knowledge.  We are receiving more and more requests to use our fluid specimens (birds) for CT scanning projects, some of which require staining.  In the recent past, we have been asked to approve two different staining techniques.  One is a 'water' based staining method and the other an 'ethanol' based method.  We would like to hear opinions about which method is best for the short and long term care of the specimens.  As with any old collection, the exact methods of fixation used over the last 100+ years have been variable, but typically our birds were fixed in formaldehyde and then moved to storage in 70% ETOH.  I'm sure some of our oldest specimens were never properly 'fixed' since formaldehyde did not come into use until the early 1900's.

The two methods:


I2KI (potassium iodine and iodide) is dissolved in water and makes a naturally antimicrobial solution in which the specimen is removed from ETOH storage and soaked for weeks to months, depending on the size of the animal, in this water solution.  Pickled tissues (fixed in formalin and preserved in 70% ethanol) should remain pickled even after being removed from preservative due to the chemical changes that occur during fixation, and iodine prevents bacterial growth, but it still involves putting a pickled specimen in water for an extended period.



I2E is elemental iodide dissolved in 100% ethanol (200 proof), which raises another set of issues for specimens stored in lower concentrations of ethanol. Increasing the concentration of ethanol further dehydrates and shrinks the specimen, but it has been found to be the most effective concentration of ethanol for staining soft tissues.



So, the question is:  Would you rather have a specimen removed from 70% and stored in a water/iodine solution for weeks/months or stored in 100% ETOH for a similar period or neither?  What are the pro/cons of each?  Would you allow a specimen collected pre-1910, and presumably not fixed, go into water/iodine for a month or more?  Are you aware of other methods?



I look forward to hearing your thoughts!



Chris


Christopher Milensky
Collections Manager
Division of Birds<https://urldefense.proofpoint.com/v2/url?u=http-3A__vertebrates.si.edu_birds_&d=DwIFAg&c=cjytLXgP8ixuoHflwc-poQ&r=LpYc_Z_iN1KRw0hheb3x6-8MJUMu482qfHowpGYJqwc&m=_ng57dMSlpRtwx104LoLynttAJTY-hHusbDzZvPHtcM&s=GUIwF2jcK-a5sAF-jpiFUFCe2_UmI54Q-akmUeSa6xE&e= >
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SMITHSONIAN INSTITUTION
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