Katrina,
           working in a dental school we don't stain many sections of uterus
The differentiation you refer to could be a result of too acidic a trichrome
stain or oxidation by components which  will convert  Hx to tri- tetra- or
pentoxy-hemateins. The tetroxy hematein is usually brownish (depending on
mordant) and the pentoxy is colorless. This is time dependent so that if for
example you stain 7 micron sections with van Gieson for 3 minutes the Hx looks
great, if for 5 minutes (often necessary for teeth) then the Hx will often
appear brownish or wishy washy. t
This may depend on which variant of Mason trichrome that you are using.
I cannot believe that the picric acid in Bouin's is causing the problem unless
there is so much of it left in the section that the Hx is becoming over
oxidized. You can remove the picric acid by soaking in 70% ethanol (with a trace
of lithium carbonate) .
            Have you considered using celestine blue instead of iron
hematoxylin? Celestine blue is much more resistant to decolorization than iron
Hx which is essentially over oxidized in many of the trichrome stains. We have
used celestine blue routinely as a nuclear stain in  van Gieson staining.
If you wish I can send the method for staining
Barry

Katrina Knott wrote:

> We have been working on a the Masson's trichrome stain on human uterus.  The
> stain looks nice but we are not getting nuclear staining.  We are using
> Weigert's Iron Hematoxylin.  It seems to look well when we apply it, and
> when we take the tissue out of the stain.  Is it possible that we are losing
> staining is subsequent steps due to the acidity, etc?  What can be done
> about this?  Increase the mordant concentration?  Change one of the other
> steps in the procedure?  It seemed to stain when we did not use Bouin's to
> post fix... but then the other dyes did not look well.
>
> thanks,
> Katrina