Preventing Condensation on Cover Slips
How do I prevent condensation on cover slips?
Condensation on your cover slips can easily ruin your crystallization setup. The fact that this may occur after a number days/weeks/months of protein preparation can make this event especially aggravating.
I recently came across a number of posts by Partrick Stewart from Douglas Instruments. I have combined and modified the posts and hopefully provided a sensible thermodynamic explanation. Finally, I have also included a tip to prevent condensation from occurring.
1. If you have condensation, then you MUST have a heat flow, where the heat is flowing to where the condensation occurs.
2. The solutes in the reservoir will stop condensation due to minor heat flows. The more salt etc, the less condensation on the tape.
I find the easy way to think about condensation is to remember that wherever there is a heat flow, that flow carries moisture with it. (Or you could think of it as the moisture carries the heat, although obviously it is the heat flow that drives the process.)
Therefore, when you put a warm plate in a cold-room, heat will flow UPWARDS from the reservoirs into the air above the plate, and you’ll get condensation on the tape or cover slip.
The simple solution is to put a (warm) book from your office on top of the plate when you put it into the cold room. Now you have a heat flow DOWNWARDS from the book, through the plate and into the cold bench.
This method is guaranteed to prevent condensation – in fact it will remove condensation if you have it – just put a warm book on the plate.
I haven’t experimented with the size of book – it could be that I have been actively drying out the drops, which may not be so good!
And I’m sure that other objects would work well although I have only tried books. They seem ideal because they have a reasonable thermal mass but quite low thermal conductivity.
Finally, you will have a use for those Harry Potter books.
Mark
April 21st, 2009 at 7:47 AM #
You can also prevent condensation by cooling your trays prior to setting them up. For a VDX plate, place the tray (covered by a “blank” tray which is also at room temp and contains H2O) in the cold room for 25 minutes or more prior to setting up the actual drops. Cover slips and sealing tape should also be placed in the room prior to set-up.