When I suggested cervix for a PAS control - I intended it for use as a 
glycogen control.  Kidney is the most sensitive control for the reaction - as 
there are fewer reactive sites.  I weakened reaction can be determined very 
quickly.  I think I said before on histonet that we stained a multitude of 
kidney biopsies - and to  be certain that the results were good - we used a 
staining jar of reagent for two batches of slides only.  Whoever poured the 
reagent into the jar, could put it back in the refrigerator (and we always 
refrigerated).  If you got it from the refrigerator in the staining jar, then 
you dumped it after use.  We could always tell when someone tried to "cheat", 
because the results showed a decrease in staining.

As Rande indicated, small intestine is a good control for mucin, but it is 
not as sensitive for the quality of the reaction as kidney.  And it goes 
without saying that a section containing fungi should be used for the PAS 
reaction on tissue suspected of containing fungi.

Several of the histochemists - Troyer, Vacca, and I think Lillie - state that 
because the water supply in many cities is heavily chlorinated and will 
reoxidize the Schiff reagent if you go directly into running water - it will 
increase the possibility of false staining - so I think that the sulfite 
rinse is probably a good idea.

Freida