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. Re: 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 too. Merely suggestions and good luck Gayle M. Callis HTL(ASCP) HT, MT Bozeman MT _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet