Re: over cooked. There is hope.

From:John Kiernan

You might be pleasantly surprised. I have left
specimens for a few days in hot wax on many occasions
and never noticed any difference from ones that had
correct (hours rather than days) infiltration times.
The specimens were always thoroughly fixed (at least 2
days, usually 7 in buffered formaldehyde or much
shorter times in several of a variety of more rapidly
acting fixatives, all traditional). They were also
thoroughly dehydrated, either with plenty of changes of
100% alcohol or chemically with acid-catalyzed
2,2-dimethoxypropane. Nearly all this is traditional
wisdom dating from long before I was born and published
in numerous articles and books, both ancient and
modern. (DMP is younger, only about 35 years old.)

If your specimens were inadequately fixed in an aqueous
formaldehyde solution such as PBF they have probably
been damaged by the solvents and perhaps also by the
long stay in melted wax. Inadequate fixation in aqueous
formaldehyde means less than about 24 hours. That's a
lot less than the ideal time, but it has been accepted
as sufficient by pathologists, probably because the
late Ralph Lillie 
said so in his influential textbooks.

The bottom line is that you should look critically at
some stained sections of a few of your specimens that
had a few days in melted wax. If they are OK, go ahead
with them all. If they are awful, find out who ordered
unduly short fixation times and ask why.
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
"P. Emry" wrote:
> I processed some bone tissues and let them harden in the last paraffin
> bath.  I had a week off and after severl days back on the job I found the
> heat had been turned on on the specimens.  I have no idea how long they
> have been cooking.
> I am going to embedd them today, but wondered if there was something I
> could do to undo damage done by so long in heat and paraffin.
> Thanks,
> Trisha

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