Joyce,
I have never used tissueprep, however the problem you are describing is
very familiar. We see the exact same sectioning difficulties if the
paraffin temperature is too hot for too long in the holding pots. Since
we use large amounts of paraffin we pre-melt it in old lipshaw paraffin
pots so that we can rapidly supplement the paraffin in the small wells
of our embedding stations. technicians figured it was easiest just to
leave a thermometer in the pot with the bulb at the bottom to monitor
temperature. But guess what? Heat rises. The temperature of paraffin in
the top of the pot was well over 75C. This causes the hydrocarbon
chains to "crack" which is how petroleum is refined but a terrible
thing to do to your paraffin. The comparison to paraffin contaminated
with xylene is appropriate, because "cracked" paraffin will have
solvent properties similar to xylene.

Bert

On Thu, 12 Nov 1998 12:01:54 -0500 Joyce Friedland
<joycefr@frontiernet.net> wrote:
> Our sections are "exploding" in a way similar to
> blocks that are comtaminated with xylene. As a test we tried cutting some
> plain paraffin blocks (no tissue) and saw the same problem.
----------------------
Bert Dotson, MBA, HTL
amdj@acpub.duke.edu