No-pour agar or pouring agar in still air box?

tonight I poured agar into petri dishes (jars) in a still air box for the first time. I feel like I might have contaminated things (felt strange leaving the jar with agar liquid open for so long in the SAB), but will see if the dishes get contaminated.

anyone ever do the the no-pour method with agar? pouring the agar in the jars before sterilizing, and then just sterilizing all the jars, with agar already poured?

seems like it might mean less contamination, but is there a reason not to do it that way?

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I use a bottle with a narrow neck and opening to sterilise and pour agar (like a wine bottle or mini-version of a wine bottle). The small mouth reduces the chance of contaminants falling inside, while also making it easier to pour smoothly and accurately. If you’re working in a SAB with good technique there’s very little chance of contaminating your plates while pouring.

I’ve used the no-pour method with mixed results. The main thing to be careful of is ensuring the stack (of plates or jars) is not able to fall over, either during the sterilisation run or during the cooling phase. There is also the risk of boil-over (where the agar escapes the containing vessel(s)).

The no-pour method does offer some advantages: no waiting around to pour the plates, no danger of burning your hand while pouring the hot agar, no chance of contamination prior to inoculation.

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I made a batch of no-pour malt-extra agar jars this weekend. It seems to work well in the pressure cooker (not falling over or boiling over).

I used a recipe of:

  • 500 ml distilled water
  • 10g agar
  • 15g LME

but I think I accidentally used dark malt extract (not light malt extract), from a jar that I just labelled “malt extract” (lol) - so the agar turned out a bit dark, but lets see if it still works… :slight_smile:

the jars look ok to me, but I’m somewhat concerned the medium may not be homogeneous, and that some of the agar or malt extract might be sinking to the bottom? this is my fear with the no-pour method, although I don’t know if its warranted, or if there’s a way to avoid it

image of no-pour agar jar which I might be phantom imagining that there is a sort of non-even “sediment” on the bottom

image of a stack of no-pour agar jars

image of how I prepare the lid for an agar jar

also have to say I’m tempted to buy some glass petri dishes,
just to have cultures which are slightly easier to see inside of

with the jars with the no-pour method, there was some condensation,
and its possible to see inside, but its not the best view

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Glass petri dishes are awesome. They’re pretty easy to clean and you can stack a lot of them in a small volume (good for sterilisation and storage purposes).

My local sushi place dispenses soy sauce in small plastic containers for take away orders. They’re round, have a snap-on lid and are made of PP5 plastic (meaning they have a high melting point and can withstand pressure cooker runs). Maybe you can find something similar in your area. They make great petri dishes and you can see through the lid (though it’s not as clear as glass).

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