Storage of Freezing Media - (Mar/01/2010 )

Where should freezing media be stored? Our freezing media are usually composed of 5% DMSO, 20% FBS, and 75% complete growth medium. I keep them at room temperature for months. However, I've read in some protocols that freezing media should be kept at -20C. What is the proper storage of freezing media? I am hesitant even of storing them in 4C since they contain DMSO and will freeze right away. If at -20C, should I aliquot them to prevent freeze thaw cycles? What do you do in your lab?

I usually make the freezing media fresh. But any leftovers is stored at -20C. I haven't freeze thawed, freezing media for more than once.

I store ours at -20, but I bought it premade.