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I understand that they are generally "vented", but why such a poor fit? For the batch I bought, the lid and container don't even recognizably go together (like 1/2" difference in diameter). The wind from a box fan could blow the lid off. Even "non-vented" designs appear to have no positive connection between the dish and lid.

Then it looks like the people that do need a positive connection or a seal have to go through a lot of work with tape or wax to seal them.

Seems like a petri dish lid that has a snap, thread, bayonet, or even just friction fit, would be superior. The manufacturing cost differences would be negligible. What am I missing? Thanks!

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    $\begingroup$ I would dislike friction fit because I would likely need two hands to open it, whereas now I can just take the dish in one movement, have my tool in the other hand, do the thing, then put it back and pick up the next one. But for storage I often tape them together by 5 for ease of handling, and that prevents accidental opening. Not too much work IMO. $\endgroup$ – Eliane B. Oct 1 '18 at 10:02
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    $\begingroup$ "Seems like a petri dish lid that has a snap, thread, bayonet, or even just friction fit, would be superior" – Petri dishes work by creating a sigmoid path that any particle would have to travel in order to get inside, which is why you don't need a tight lock. From a practical point of view you are supposed to handle (open) Petri dishes in a controlled environment with a rising air flow (preferably in a box or within a small radius of a burning flame) and you should be able to do it with a single hand, because your other hand would be holding something else in the process. $\endgroup$ – Eli Korvigo Oct 1 '18 at 12:56
  • $\begingroup$ @EliKorvigo, Now I'm curious. Do bio labs really use rising air? I know clean rooms for semiconductors use downward air to help sweep heavier than air particles and bacteria out of the environment. en.wikipedia.org/wiki/Cleanroom#Air_flow_principles $\endgroup$ – ericnutsch Oct 2 '18 at 2:37
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    $\begingroup$ Not entire labs, of course. The laminar boxes generate a laminar airflow directed toward the operator, i.e. a rising airflow. As I've mentioned before, in the old days people used to work within a very small radius from alcohol burners for the same reason (rising airflow). Additionally, old-school microbiologists never fully remove the lid: they use the same hand to rotate the plate and hold the lid above the plate, so that there is only a narrow opening between the lid and the plate during plating. $\endgroup$ – Eli Korvigo Oct 4 '18 at 14:13

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