I was a little surprised that more people didn't pick up on this--thinner 
slides (ex: 3 microns) need to be stained longer....there just isn't the 
amount of cellular material there to absorb stain....also, years ago when the 
special stains were developed the ability to cut sections at 3 microns had 
not been achieved..therefore, the times used in the stains were all developed 
for those 5 micron sections....