Spirit Collections

[John Simmons]

Regarding the recent inquiries about substitutes for formaldehyde in
fixation and preservation--in short, there aren't any good substitutes.
Formaldehyde is a good to excellent preservative for most tissues, but
not a good preservative for most tissues (there are exceptions, of
course).  Formaldehyde safety regs are not that hard to deal with--there
are formaldehyde resistant gloves, tyvek aprons, and respirators on the
market.

Ethylene glycol (a component of Caro-safe) is not really that safe. It
can be absorbed through the skin and is toxic.  There can be concentation
problems in solution, as ethylene glycol is extremely hygroscopic.  More
to the point, there are no published reports (that I have seen, at least)
on the long-term effectiveness of ethylene glycol as a preservative or
as a component of a preservative.  Thus, I would urge EXTREME caution in
using it until its effectiveness can be determined.

We have about 300 years experience with ethyl alcohol, and about 100
years with formaldehyde, and there is still a lot we do not know about
how the function for fluid fixation and preservation, so I think it is
wise to be cautious about switching to new substances without thorough
testing and evaluation.

Before using Caro-safe or other proprietary solutions, ask for the MSDS
and check it first. Many of these compounds are not much safer than
formaldehyde, just less regulated.

John Simmons
Natural History Museum
University of Kansas
jsimmons at kuhub.cc.ukans.edu