Arkyhog said:

My instant pots pull a vacuum after cooling naturally without force ventilation. There is always a suction when removing the lid from the base.

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BeefSupremeJr said:

hm.  guess  i never considered condensation.  so the volume of steam decreases, but at the same time the vessel decreases in volume as the aluminum cools.  one would think it would equalize but i dunno guys.  i think im wrong and ill retract my statement and maybe it creates a slight vaccuum but i guess i still think its moot.  you open the thing wide open, afterall.  i have a hard time believing this is why the plates contammed. call it a hunch.

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1NFIN8 said:

Ideal gas law PV=nRT

The only way a vacuum will be created in a sealed container is through a chemical reaction that reduces the n of gas molecules or the T changes.

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sloug said:

BeefSupremeJr said:

hm.  guess  i never considered condensation.  so the volume of steam decreases, but at the same time the vessel decreases in volume as the aluminum cools.  one would think it would equalize but i dunno guys.  i think im wrong and ill retract my statement and maybe it creates a slight vaccuum but i guess i still think its moot.  you open the thing wide open, afterall.  i have a hard time believing this is why the plates contammed. call it a hunch.

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on the topic of homies plates, yes probably irrelevant. the debate, i think, was moreso just the function of the presto pc itself. u vent the air out. cooker fills with steam. as the cooker cools, the steam returns to water. however theres still no, or very little, air inside it. so since the the lid is not airtight at zero pressure, the space inside the cooker is immediately replaced with the outside air. opening the lid is not when the room air enters. unless u open it exactly at the point it reaches 0psi

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BeefSupremeJr said:

interesting.  never thought about it.  never had to but i dont do pours. i still dont think that could be the vector.  tons of people do glass the same way without this being an issue.

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I do glass no pours. My AA pulls a vacuum on cool down. I have to remove the weight, let it suck air for 20 seconds before I can lift the lid. Still no mold.
The only difference from OP is I use individual ziplock sandwich baggies instead of wrapping. Also, I don't wait a week, get to work as soon as I remove them.

LadysKnight said:

BeefSupremeJr said:

interesting.  never thought about it.  never had to but i dont do pours. i still dont think that could be the vector.  tons of people do glass the same way without this being an issue.

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I do glass no pours. My AA pulls a vacuum on cool down. I have to remove the weight, let it suck air for 20 seconds before I can lift the lid. Still no mold.
The only difference from OP is I use individual ziplock sandwich baggies instead of wrapping. Also, I don't wait a week, get to work as soon as I remove them.

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PC envy. I want an AA too

BeefSupremeJr said:

hm.  guess  i never considered condensation.  so the volume of steam decreases, but at the same time the vessel decreases in volume as the aluminum cools.  one would think it would equalize but i dunno guys.  i think im wrong and ill retract my statement and maybe it creates a slight vaccuum but i guess i still think its moot.  you open the thing wide open, afterall.  i have a hard time believing this is why the plates contammed. call it a hunch.

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Even without condensation, you could make a vacuum. Let's say I am fermenting 25L(26qt) in a 35L(37qt) pressure fermenter at 16°C(60°F), after fermentation is done I want to cold crash(meaning getting the beer  as close to freezing as possible to get more solids to drop out of solution before I transfer the beer to a keg).

So I set my fermentation fridge to 2°C(35°F). Just the beer alone will be reduced by about 0,3L, the remaining 10L of CO2 in the headspace will be reduced approximately another 0,5L(this is simplified because in reality some of the CO2 would go in to the beer and some condensation will occur). So now I have two options, I could either(what I do) connect a CO2 tank with a little pressure and as the CO2 and beer inside the fermenter "shrink", CO2 will enter the pressure fermenter and equalize the pressure, or, I could do nothing and my fermenter implodes, plastic might survive, but the stainless steel would be ruined

As for the contaminated plates in question, if LadysKnight's observation is correct and agar solution spilled and was on the outside of the plates, it would contaminate real fast after the foil came of. But you're right, we could never find the source, and are wasting time trying

I just wanted to get that out there as I think it's a good argument for putting foil on jars, media bottles etc during a PC cycle. Promise I'm done with this