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.

incubate inverted at 37°C for some hours. Cool down slowly to storage temperature (i.e. 37 --> room temp --> 15-10°C --> 4°C) and THEN store in slevees, otherwise you will get condensed water on the plates again.

If you are storing the plates at 4°C: let them reach the incubation temperature before seeding microbes on them, better for you microbes growth, and condensed water on the agar surface can evaporate.

Quote 'Thanks. However, I need to prepare hundreds of plates and that takes lots of time.......'

This is why we don't bother when we pore the plates. We'll dry them in the hood for about 15-30 min. before we need them.
Works for us, goes pretty quickly and the best side, you don't have to bother to dry them before you store them. Since despite all the things we tried (all the suggestions here included) we still had condensation on some of the plates..

put the agar-plates in the super clean bench, turn on the air fan, blowing them for 30mins

After pouring plates place it up side down in the incubator, this will reduce condensation.

I used to have moisture problems but with proper usage of a vent hood it's a non-issue. First, I leave the lids half-off until the plates solidify, allowing lots of moisture to escape right away. Then, I stack the solidified plates in the corner of the hood and keep pouring until I'm done. The rapidly moving air helps the stacked plates cool even faster. I give them about 20 minutes to sit there once I'm done and then invert them and put them on my bench until it's the end of the day when I sleeve them and put them in the incubator (inverted) at 37C. This will not only get rid of extra moisture out of the plate but it will tell you if you've got contamination -- IMO, I don't used just-poured plates since there might be something on them that will grow when I plate my experiments, and that's a horrible time to find out that you've got contamination.

If you're doing spread plating it's also helpful to leave the plates in the hood, lid ajar, until they dry of all visible liquid on the agar surface that you introduced during plating.

Doing those things, I have no problems with plates being too wet.

If you're in a huge hurry during the day (ie. - you can't get the extra few minutes in the hood that my suggestion requires) you can put a slit in the sleeve so that during overnight incubation the plates lose more moisture than in a well-sealed sleeve. This is last-ditch, though.

Hi,

How many days one can use the colonies on argr plate? I streaked the plate like 2 months ago. I donno if I can still use the separated colonies on it ?

The agar plate looks little dry but not completely dried.

Thanks