Cracked SSCP gels

[r.j. dewar]

	Can anyone tell me why my polyacrylamide gels are cracking while drying?
I have been running SSCP gels on 10% polyacrylamide gels, some containing 
10% glycerol and some without.  As with most problems, things have been 
going well for some time, and then the gels started to crack when I 
removed them from the gel dryer. 
	Is it too much heat, too much vacuum or too much time?  I dry 
them for 1 1/2 hours at 65 C.

	Thanks for any suggestions.

	Roger Dewar