[3dem] Thinner ice after several microscope uses

[Eduardo Sanz García]

Henning Stahlberg wrote:
> Hi,
> 
> We had a similar phenomenon: Ice contamination on cryo-EM grids was 
> sometimes but not always quite bad, but the second inserted grid was 
> often less contaminated than the first one. This was on a JEOL JEM-2100F.
> I believe the problem might have been related to some weird air-pocked 
> formation in the goniometer, potentially between two consecutive O-ring 
> sealings. When we left the goniometer without sample holder over night, 
> air might have slowly accumulated somewhere and was inserted into the 
> column during the first sample transfer. We tried leaving a holder in 
> the goniometer over night, but that did not significantly improve the 
> situation, as if the "leak" only occurred during sample insertion.

I was thinking in the same lines than you, a problem with the 
goniometer-airlock, but yesterday, I had another idea of what could be 
wrong.

If for some reasons the cool trap takes a lot of time to cool off, like 
  1 or 2 hours, the cryoholder could function like a cool trap building 
contamination in my grid. On the other hand, if the microscope have been 
working all day long, then all the contaminant have been trapped during 
the day, then I will not have problems of contamination.

Two questions for everybody:

* How long do you let the cool trap to cool off before inserting the 
cryoholder?
* Is it necessary to do a cryocycle every night?

Thank you very much.