We always fix with NBF, better morphology, and retains the water in
cartilage, then process through 70% ethanol, 80%, 95%, and 100% 2 changes
each  (whole rat knees 2 hours per change) then 1 change xylene, and
1 change Clearite 3 or Propar, 3 - 4 changes Tissue Prep 2 (Fisher),
embed in same.  The slides are picked up on Plus charged slides,
dried FLAT at 37-40C overnight but usually for several days, in an
incubator is great.  Prefer to section with the sharpest knife or
disposable blade possible for the flattest section and often increase the
temp of waterbath a few degrees to flatten section (but not "explode"
section.

If there is a problem, presub regular uncoated slides with Chrome
gelatin, OR even add a FEW granules of 275 bloom gelatin to the
water bath.  I have even made up the chrome gelatin subbing
solution and added 10 mls to a water bath.  All work well, prefer
the plus charge, but make sure you drain the water from bottom of
section (in upright position)BEFORE laying flat with these specially
coated slides.

Good luck,
Gayle Callis