We routinely cut transverse sections at 1 micron of rat peripheral nerves
for Neurotoxicity studies embedded in Araldite resin. We float out on
distilled water and dry on a hot plate before staining with toluidine blue.
Unfortunately we often find that the sections don't flatten well and appear
to trap small air bubbles beneath the sections. This doesn't happen with the
longitudinal sections from the  same nerves. Any tips or comments please.