Agar in plates is contracted after storage and 1 mL of water appears. Any tip? - (Mar/26/2013 )
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
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.
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.
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
phage434 on Tue Mar 26 13:06:21 2013 said:
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?
It just keeps the top of the plate warmer, reducing the amount of condensation from the hot agar.
phage434 on Thu Mar 28 03:33:59 2013 said:
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...
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.