Carnoy’s fluid is a very rapid fixative and has been used frequently for fixation when rapidly processed paraffin sections are wanted. For a 1-2 mm piece of tissue only 30 to 60 minutes is required, and dehydration takes place at the same time. It is a good nuclear fixative, but produces considerable shrinkage and cytological distortion. As with most alcoholic fixatives, glycogen is preserved well.

This is the fixative usually meant when “Carnoy’s fluid” is specified. There is another fixative often ascribed to Carnoy, a 3:1 mixture of ethanol and acetic acid, but that is more correctly referred to as Clarke’s fluid.

Time

30 minutes to 2 hours.

Aftertreatment

Transfer to absolute ethanol.