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Agar in plates is contracted after storage and 1 mL of water appears. Any tip?


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7 replies to this topic

#1 luisv

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Posted 26 March 2013 - 03:16 AM

Hi,
I have a problem with my agar plates (chlamydomonas media, pH 7.5). I pour 30 mL of agar in the plates, wait until agar is solidified and keep them drying for 30 min in the hood. Then I seal them with parafilm and keep the plates at 4C. But when I take the plates out from the fridge the agar is contracted, with a diameter of the agar disc about 2 mm shorter than the inner diameter of the plate. Do you have any idea of what is happening?
Thank you very much,
Luis

#2 phage434

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Posted 26 March 2013 - 05:06 AM

There may be special issues with this agar -- I'm not familiar with it. But in general, it works best if you cool the agar to 55 or so before pouring plates. Also, placing an empty plate on top of a stack of newly poured plates helps reduce condensation.

#3 Rahaf_Issa

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Posted 26 March 2013 - 01:11 PM

It sounds like your plates are drying out. We store our plates without wrapping them in parafilm and have never had any problems. It's probably worth a try.

#4 El Crazy Xabi

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Posted 26 March 2013 - 03:04 PM

Some labs recommend let dry the plates overnight on the bench to reduce condensation. I did it and it helps.
30 min after solidification, plates will still be quite warm so, a fast cooling will affect to the condensation and also may affect to the shrinking.
Also, as phage434 indicates, it is recommendable to cool the agar down to 55° C before pouring.

By the way, how long have been the plates in the fridge? If you leave them for some long time is normal that they shrink

#5 lyok

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Posted 27 March 2013 - 09:51 AM

There may be special issues with this agar -- I'm not familiar with it. But in general, it works best if you cool the agar to 55 or so before pouring plates. Also, placing an empty plate on top of a stack of newly poured plates helps reduce condensation.

Interesting.

Do you have any idea why an empty plate can prevent condensation in other plates?

#6 phage434

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Posted 27 March 2013 - 07:33 PM

It just keeps the top of the plate warmer, reducing the amount of condensation from the hot agar.

#7 lyok

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Posted 27 March 2013 - 10:19 PM

It just keeps the top of the plate warmer, reducing the amount of condensation from the hot agar.

How do you mean : it keeps the top of the plate warmer?

I do not see how putting 1 empty plate on top of some freshly poured plates keep the poured plates hotter at the top...

#8 phage434

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Posted 28 March 2013 - 03:32 PM

The empty plate acts as an insulator. Anything else that is an insulator would work, to slow down the cooling of the top-most plate (specifically the lid of the top-most plate). Empty plates are just convenient and re-usable.




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