[Histonet] RE: Ice build up on

gayle callis gayle.callis <@t> bresnan.net
Tue Jun 23 11:19:43 CDT 2009

You wrote: 


We purchased a Leica CM1850uv cryostat in 2007 and we constantly have
problems with buildup of ice on the specimen metal bar.   This causes the
tissue to stick to the

stationary heat extractor which causes significant problems cutting frozen
sections.  The engineer has serviced the machine several times, but
recognizes this as "normal ice buildup".


We manually defrost the unit 2-3 times a day, but it does not seem to help.
Is anyone else experiencing the same problem, and if so, what are they doing
about it?  Thank you.



By manually defrosting the "unit", do you mean using the mini-defrost
command for the cold bar area and not the whole cryostat?  We have used that
command to clear ice from holes but it tends to get really hot.  After this
is done, the melted ice water is wiped away with 100% alcohol damp gauze IF
the water is apparent/obvious since it will simply refreeze and cause ice
buildup again.    Consequently, we have not used that mini defrost mode too
often but rather do the following.  


To get rid of the ice out of little holes and off cold bar, use a  Q tip
dampened with 95% alcohol in holes and a 95% dampened gauze on flat
surfaces.   Since alcohol is an antifreeze we can eliminate the ice without
heating up the bar area.  Also wipe the underside of the heat extractor to
get rid of any ice crystal build up located there.  If 95% is not working
well, use 70% followed by  95% or 100% to get rid of any residual water left
from the 70%.  The main thing is to clean the bottom of heat extractor more
often and just before freezing since the ice crystals are messing up
cryotomy.  Just don't get alcohol on your tissue by wiping underside with
dry, RT gauze after the alcohol wipe.   


One, be sure to minimize adding water to the cryostat - sometimes difficult.
This can happen when cleaning with 70% alcohol that is dripping off gauze or
normal usage.   If one dampens the gauze for cleaning and wipes down
interior - buildup is minimized.  If you see too much 70% then wipe again
with 100% to help dry the surfaces before you turn on the UV light.  


Also, major defrosting of whole cryostat may have to be done more
frequently.  We raise the removable metal plate and check for excessive ice
buildup under the and the back of chamber and defrost the whole cryostat if
the ice begins to look like our Montana winter.   We live in such a dry
climate that frost buildup is minimal, but high humidity days are factor


Merely suggestions and good luck


Gayle M. Callis


Bozeman MT 










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