Jason Wiese notes:

Presto-fixe II Active ingredients:

1.0 Molar Formaldehyde
0.2 Molar Glyoxal
60% Methanol
Buffer
PVP [polyvinylpyrrolidone?] (macromolecular colloidal membrane 
protectant)

This is a totally irrational proprietary formula of the sort John 
Kiernan used to rail against - where's John now that we need him? If it 
works as a disclosing fixative or postfixative, it's because it 
contains an alcohol and formaldehyde. Neutral buffering isn't desirable 
with such fixatives, but who knows what pH it's buffered to? - The 
glyoxal is an additional aldehyde fixative, and I can think of no 
reason to mix them - you probably get the disadvantages of both. People 
have put things like PVP and middle range Carbowaxes into fixatives for 
a long time, but I'm not sure they do any good. - You have no way of 
knowing how the fixative supports immunohistochemistry, and it would 
take long and expensive trials to find out - and wouldn't be FDA 
approved for breast cancer anyway.

Methyl salicylate (oil of wintergreen) and cedar oil were once 
recommended as disclosing fixatives, but they aren't practical - 
time-consuming, expensive, smelly, and sometimes toxic.

Bob Richmond
Samurai Pathologist
Knoxvill TN
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