John (and others),

Interesting comment you made about the time to stain plastic 
sections.
I always believed plastic sections were stained for longer because 
there was less "substrate" and time was needed to "get at" all of it.

Of course, your comments about thicker plastic sections taking 
even longer knocks that theory into a tin hat!  Those of us who have 
only stained thin sections would have been unaware of the 
penetration problem, but should have thought of it.



One could also believe that almost all there was to stain would be 
stained in a shorter time in thin sections.

Ergo, the penetration reason must be the prefered one.
Russ Allison, 
Dental School
Cardiff
Wales