Dear Renee:
I agree that the block is too cold. Probably because you went from -80 to
-20 too quickly (in other words, 2 hrs is not long enough). We have found
the same problem when we fix in isopentane at dry ice temp. We have to let
the block sit in a -20 freezer overnight before it is appropriate to cut.
Now I freeze in the cryostat, using only some dry ice powder to speed up
freezing, so I don't have to wait that long. 

I am actually looking hoping this list will give me some better freezing
methods. The isopentane is too cold and a lot of my blocks crack. 

Sarah Pixley

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