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condensation on agar plates - what happens if it drops in the plate while plating (Feb/10/2009 )


I'm having trouble cloning and recently condensation from the lid dropped inside the agar plate as I was plating my transformed cells. I didn't get any colonies. Thus would the condensation have caused any problem and how should I avoid it in teh future. I do store my pates upside down but just before plateing, I turn themteh right side up for 10mins.



This is how I pour my plates

The lid of the plate is lifted just high enough to allow the plate to be poured, and the dish is quickly half filled with agar. #The lid is REPLACED, the plate swirled gently to ensure even distribution of the molten agar, then left to stand on the bench for at least 20 minutes to solidify. The plates are then stored upside down in fridge.

I do see condensation after teh plates have solidified and just store them upside down in the fridge. The condensation on the plates after teh agar solidifies and just before I store the plates in the fridge, a problem?


Condensation dripping on your plate would not have stopped your transformants from arising. At worst, it might have introduced a contaminant that could also grow, but your correct colonies should have come up as well. Most of the time the condensation is sterile, and only causes problems if you're trying to plate well-isolated colonies, as it might cause some of your careful spreading to be for naught.


I leave the plates open after pouring them for 30-45 min. before placing the lid back. Then I close them and leave them on bench for 1 day before having them in 4C.

But the condensation should not affect colony growth. There is some problem with your ligation or transformation.


Agree with the previous posts: the condensed water does not effect you cloning exp.

Two other problems can be caused by condenstation: 1. that the plate is "sealed" by a water film between the lid and the bottom of the plate. But this problem does not occur when are not incubating your cells long enough that they use all the air.
2. it drops on your plate and your microbes begin to mix as they are spread all over the plate by the water film....

Therefore: carefully prepare your plates and let them dry....for tips on agar plates see here


A tip to pouring plates and avoiding condensation is to remove the agar from the autoclave and place in an oven at around 55 C, but no lower than 50 C first to cool.

This allows the agar to cool sufficiently that when it is poured no condensation will appear (or only on the top plates of a stack of them) as the heat coming off them is not high enough.


Cotchy is correct -- cooling the agar solves many of the problems. And you can eliminate most of the condensation on the top of the stack by putting an empty plate on top.