[Histonet] over and under processing

[Steven Slap]

Hi HistoNetters

Louise Renton wrote:
"However, anecdotal evidence has stated that these tissues may become
'alcohol-fixed" thus making them difficult to cut. What is the rationale
behind this?"

In my experience, this is caused by under fixation.  Formalin is a very slow
acting fixative (it penetrates at a rate of something like .7mm/hour, then
still needs to cross-link the proteins), so, in many cases, tissues are not
totally fixed when they reach the alcohol steps in processing and are fixed
by the alcohols, leaving distinctive alcohol-fixation artifacts (shrinkage,
dryness, etc).  Therefore, what many people tend to call "over-processing"
turns out to be under-fixation.

best regards,
Steven Slap