People studying fish systematics, ecology, etc. allow for about 10% 
shrinkage in standard length for specimens preserved in formalin. 
It's a ballpark estimate. Otherwise, tissue shrinkage is too 
dependent on tissue type, how many different tissues, fixation times, 
and so forth to give a specific formula. Plus, shrinkage depends on 
mechnochemical properties of tissue that vary with the x/y/z 
dimensions. For instance, fibrous tissues will generally shrink 
differently along the fibers than across the fibers. Think of how 
wood -- a cellulosic, fibrous tissue -- cracks on drying: differently 
along the grain than across the grain.

The best bet is to take the tissue you're working on and do the 
empirical experiments using the conditions in which your tissues are 
fixed. Then publish the results in the NSH journal or the like so we 
can read them.

Phil

"Jennings, Margaret A." <jennings@mayo.edu> wrote:
>  What is the formula for shrinkage when using 10% neutral buffered formalin
>to fix  a tissue sample? If I start with a tissue a microns x  b microns x c
>microns what do I end up with? Is there a time factor for additional shrink?
>Is there also a formula for rate of penetration? Formalin infiltrates y
>microns per t? What about other fixatives any formulas available?

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Philip Oshel
Supervisor, AMFSC and BBPIC
Dept. of Animal Health and Biomedical Sciences
University of Wisconsin
1656 Linden Drive
Madison,  WI  53706-1581
voice: (608) 263-4162
fax: (608) 262-7420 (dept. fax)