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81Renaissance said:
Or some vendors sell dishes that are sterile until you open the packaging...those also need not be sterilized...if they are already sterile, they will say so on the packaging

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RogerRabbit said:
Plastic petri dishes are not PC'able.
RR

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Here's how to do it. Get a whiskey or wine bottle with a screw on lid that will fit in your PC. Drill a hole in the lid and stuff it with polyfill or cut a synthetic filter disk to fit inside the lid. Prepare your agar and pc in the normal way. The filter will prevent contaminants from entering the agar as it cools.
Build a glovebox. You can make one for the price of a clear rubbermaid. All you need is a couple of arm holes. You don't even need attached gloves, but if not, then be sure to wear latex gloves when you pour your dishes.
Allow the agar to cool almost to room temperature without opening the filtered whiskey bottle it's in. When it is cooled off, but still liquid is when you want to open it up to pour. Work fast. Open your sleeve of presterilized dishes just before use. Wash the outside of the sleeve with alcohol before opening carefully from one end.
Stack your dishes in two piles of ten. pour the bottom dish by lifting the entire stack, then set it down and pick up the other nine. Repeat until you've filled both stacks, then CAREFULLY insert the sleeve back over the petri dishes and seal the bottom so it's airtight.
The above procedure should give you a 100% success ratio with a bit of practice. I find no difference in contamination rates with a glovebox or flowhood, but of course the flowhood gives you more elbow room and is much easier to work in front of.
RR

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