problems with agar-plates: tips - (Oct/19/2004 )

Since the plates have some water on them, so after incubation, the microorganisms grow together or spread, and i cannot count!
that is bad.
i know if you can cool the plates down completely, it will be better.
how ever, it costs time!
can you give me a suggestion about how to plate quickly(cool down) and no water residue and no spreader problem?
thank you

* Cool agar to 50-55 degrees before pouring your plates. This has the largest effect.

* Put an empty plate on top of the stack of poured plates to minimize condensation.

* Leave plates out overnight to evaporate, or put plates in the incubator for a few hours

* you can switch sterile plate tops with condensation with another empty sterile plate

I presume you are putting the plates into the incubator upside down, which will minimize the
moisture spreading cells during incubation.

Thank you Phage434, very usuful tips for the common problem.

and one more, if you are in a hurry and have a good sterile hood: leave plates open in hood till dry (usually 10 to 30 minutes).

Thanks. However, I need to prepare hundreds of plates and that takes lots of time.......
Another question:
How long would you keep plates(prepared)?
in room temperature how long?
at referigerator how long?

that could depend on the kind you are using...

Most kinds should be good for a few weeks at least whether kept at room temp or refrigerated. If the plate's gone bad you usually know it - it looks dry or contaminated.
refrigeration is especially important for rich plates (like LB), which become contaminated easily, or plates containing antibiotics which may break down (ampicillin especially is "famous" for this).

Pour plates, allow to cool to set up, invert overnight at room temp. Then store inverted in slevees.