lids, up or down? - (Feb/02/2007 )

Hi, silly question, I know.

How do you put the flask lids on your hood when you are working in a cabinet? I've seen people doing different ways. Some with the part that touches the flask open to the cabinet air which is suppose to be clean and others just the opposite arguing that the air may be contaminated and the hood should be clean because of the ethanol you use in it each time.

What you think? Why should I do it your way?

Down - I am always worried that something might fall into the lid!
mito 1

I usually have the lid ffacing up. Its just that I am used to it.

Face down

My instinct tries keeping it face up as it is easier but when I first joined the lab, I noticed my tutor always had the face down. I actually never asked him what was that about but I could reason out like what U said - somethng may drop into it. . . even a drop or aerosol may cause contamination and when U put the lid face down, the part coming in contact with the mouth of the bottle will never actually touch the floor. So, I prefer face down. So, do everyone in our lab.

Down for me. In addition to the inevitability of something falling in the upward cap, the most tissue culture flasks are designed to rest the lid open-side-down. The threads on the cap are recessed a little bit from the bottom edge, so the in the internal threads of the flaskcap will only touch the external surface of the flask. That way, even if the work area isn't super clean, bottom of the cap never comes into contact with 'sterile' internal environment of the flask, and so will not transfer any hitch-hikers into the culture.

But if you're not getting any contamination, you must be doing something right. Well, that and the Pen-Strep supplement.

I was taught (by a video from the NIH) to hold my lids in the fingers of one hand (i.e never put the lid down) and to hold the bottle on an angle to stop stuff falling in it. It is a bit of a hassle until you get used to it, but it seems to work, i've only had two contaminations in three years of cell culture

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