Years ago I worked for Columbia University in NYC. They never disposed of any 
blocks. They had long hallways lined with cabinets for blocks and slides. My 
question is, since they fix their tissue in Bouins solution, when the block 
is exposed to air it dries out. Many times, when we went back on a block 
after a few months it was caved in from dryness. So, what happens after 5, 
10, 15 years and so on. Should we practice sealing the blocks ?  What have 
other labs experienced after going back into a block after a long period of 
time.
RetTek2000