There are two issues related to the "problems" reported on 
Masson's trichrome applied to frozen tissue.

First, connective tissues are what they are called and as a result 
may be under tension, relaxed or whatever - particularly muscle.
Try pulling on a wet cloth and water will drip out.  You will have 
changed the geometry of the cloth fibres.  Same thing happens 
with muscle (and other CTs).  Unfortunately I do not have the ref.to 
hand, but will when things ease up a bit.

The "pores" or "spaces" in the molecular structure will be bigger, or 
smaller.  That means that  bigger (than usual) or only smaller (than 
usual) dye molecules can "penetrate" the tissue - or parts, or 
sections, of it.  Hence different - or at least, non- homogenous 
staining.

Ergo - what you are seeing may well NOT be artifact.

It is more complicated than that of course - the increased 
availability of binding sites for alternative attractive forces, the 
stoichiometric configurations may all change and influence dye 
binding.

Second, temperature and fixation, for example, can also have 
these effects.  In deed they do and it is easy to completely reverse 
the usual staining pattern of ALL the tricrome stains by fiddling 
about with temperature, especially during processing.

If you REALLY want to know, see Biotechnic & Histochemistry 
(1997)73;128-136.  There you can find pretty pictures, my verbose 
prose and reference to real histologists like Baker and Horobin.

Russ (with coloured fingers)

Russ Allison, 
Dental School
Cardiff
Wales