[Histonet] re:paraffin and staining problems

[Matthew Close]

I think that your problem has mostly to do with inadequate
dehydration/infiltration.  I've had this problem mainly with sections of
vertebrate skin or sections that possess lots of little blood vessels.
 Water is either unable to move through the keratin sufficiently to
dehydrate and I often acquire embedding/sectioning problems as a result.
 With the blood vessels, I think the problem is more of tissue thickness and
heterogeneity.  The thicker and more heterogeneous tissues require longer
dehydration and infiltration times, and since I prefer xylene over cedarwood
oil, I have to play the game of hard tissue vs. inadequate infiltration.  I
would perhaps try an extra fresh absolute ethanol step and add a fresh
xylene every few days/rounds or so.  At some point I figured out the right
combo.  But I still come across similar problems to what you are having, at
least with the sections cracking.  If all of the water isn't removed, you'll
get expansion/contraction at different rates than the paraffin this
resulting in cracks in the block (usually upon cooling).  I will usually go
back and reinfiltrate.  With the poor staining, it sounds like a post
infiltration problem, maybe even a post sectioning problem.  How are you
mounting sections?
-Matt