[Histonet] mordanting in Bouin's, storage in 70%, processing mouse tissues

[Wurdak, Elizabeth]

Hello,
I learned of this listserve group at the recent meeting of the Biological Stain Commission.  I wanted to join immediately because I teach histology to undergraduate students. We work through the whole paraffin technique in lab using manual methods.  We are always coming up with some questions.  Here are a few:

1.  An  attendee at the Stain Commission meeting mentioned using Bouin's fixative  as a mordant prior to Mallory staining of formalin fixed tissues.  We have been using saturated mercuric chloride in 5% acetic acid.  Is Bouin's better?  Is it less toxic?  For how long should the sections be immersed in it?  Do you post-treat with lithium carbonate to remove the yellow picric acid before proceeding to the next step?

2.  How long can you store formalin fixed tissues in 70% alcohol?  Is it best to store them at room temperature or the refrigerator?

3.  Our mouse tissue blocks are coming out brittle, dry and hard to section with the exception of lung and testis samples.  I attributed this to incomplete paraffin infiltration, but lengthening the parafffin baths has not helped.  It was suggested to me that perhaps we are dehydrating too long.  We have been using 3 changes of a 100% alcohol for 1 hour each.  What would you recommend?

Many thanks in advance for your suggestions.
Elizabeth