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Offlinebill bixby
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Re: BOD's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta] * 1
    #24594660 - 08/31/17 09:45 PM (5 years, 6 months ago)

putting that extra weight on the jiggle weight is bloody bagus
cheers lad


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Offlinetryptkaloids
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bill bixby]
    #24603610 - 09/04/17 04:28 PM (5 years, 6 months ago)

sorry if this has been asked, but why do you recommend a 10 minute vent? when I do ten minutes it's not pure steam coming out, there's still air pockets at ten minutes


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InvisiblebodhisattaMDiscordReddit
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: tryptkaloids]
    #24603625 - 09/04/17 04:35 PM (5 years, 6 months ago)

By all means go longer. I don't know how you know there's pockets or not or how pure the steam is coming out tho.

Steam/water expansion ratio is 1600:1 so after 10m of ventilation you would figure that the one volume of air has been displaced as well as it will get


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InvisibleMadHatter333
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta]
    #24659322 - 09/25/17 04:04 PM (5 years, 5 months ago)

So I know this is a old post, but I had a question. I pc'd 12 half pint jars in my presto following a lot of these guidelines. I took them out after cooling and the brf mixture seemed moist inside. I put Scotch tape over my inoc holes and tinfoil on top of the lids and it still got some moisture in there. Is this normal or am I doing something wrong?


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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: MadHatter333]
    #24659331 - 09/25/17 04:09 PM (5 years, 5 months ago)

If they go in right they should come out right unless they tipped over.


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InvisibleMadHatter333
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta]
    #24659674 - 09/25/17 06:30 PM (5 years, 5 months ago)

They stayed up right the whole time and I made sure water wasn't touching the jars. Used a layer of rings tinfoil then another layer of rings. Filled the water to the second layer of rings, placed six jars on those, placed rack on top of those jars and added six more jars on the rack. Seemed like moisture got in the tin foil and seeped through the tape a bit. I did the ten minutes of steady steam before I placed the weight on and ran it at 15psi for 90mins. Do you think it was condensation from the brf/verm mix? I made sure there was no excess water in the mix before I filled my jars.


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Edited by MadHatter333 (09/25/17 06:32 PM)


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Offlinethewiseguywithaj
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: MadHatter333]
    #24662486 - 09/26/17 07:48 PM (5 years, 5 months ago)

yo i have the presto 23qt. You know the safety lock pin that pops up once its boiling, Is it normal for it to leak steam/ water out of it?


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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: thewiseguywithaj]
    #24662506 - 09/26/17 07:56 PM (5 years, 5 months ago)

Not once its fully popped


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InvisibleMadHatter333
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta]
    #24662729 - 09/26/17 09:09 PM (5 years, 5 months ago)

mine was also leaking water out of that too. How do you avoid that? Might be why moisture got into my jars.


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Invisiblephatty
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: MadHatter333]
    #24684715 - 10/04/17 09:20 PM (5 years, 5 months ago)

Could it be that the elevated pressure above the design pressure (due to the quarters) is causing some steam leakage around the lock pin?

@Bod: Out of curiosity, what is the pressure of an ideal gas raised from room temp to 250 degrees F in a confined space? Given how close that is to 15 PSI guage, and the fact that steam and air are constantly escaping, I doubt the partial-pressure concern you raise is a significant influence. It is actually not the steam, but the temperature that matters.

I personally wouldn't risk raising pressure above what the cooker was designed to contain. And I wouldn't put grease on the seal. In fact, most cookers come with instructions that tell you this. No offense, because you're a highly esteemed contributor here, but your advice seems wrong to me, as well as dangerous. If 15 PSI isn't enough, or if your half-life for "air partial pressure" is more than say, a minute, then add a few minutes. It seems much safer than putting quarters on the pressure weight. Set me straight if I'm wrong. Just thought I'd say my piece.


Edited by phatty (10/04/17 09:21 PM)


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Offlinepotnug
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: phatty]
    #24684732 - 10/04/17 09:26 PM (5 years, 5 months ago)

I have quarters taped on the jiggler, it's convenient.


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InvisiblebodhisattaMDiscordReddit
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: potnug]
    #24684758 - 10/04/17 09:39 PM (5 years, 5 months ago)

Im not a safety ranger. If you're doing this don't be dumbass. Ive talked about the risk and greasing the seal in the pages of this thread.

Venting air is so hard to do that autoclaves have made great use of microprocessors and sensors. If the temp doesn't match the pressure it will pulse the pump to try to remove that air.

I had an old tuttnauer autoclave and it would literally take just as long to go from 248 to 250 as it did to go from 70 to 248.
Newer ones work better but it wouldn't start the timer until all gas was purged. And the internal volume wasn't nearly 23Q

The temperature of a gas raised to 15psi from atmosphere is irrelevant because its being heated by steam as well.

After the weigh is on and pressure is reached you turn the heat down. Steam should barely escape i lose only a few ounces of water after two hours. Constantly escaping isn't a replacement for the venting.

If you had a temperature probe you could put in the PC during the cycle you could figure it out pretty easy but we just try to vent obnoxiously long to ensure we're actually sterilizing at 15psi


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Invisiblephatty
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta]
    #24684871 - 10/04/17 10:32 PM (5 years, 5 months ago)

The relevance of the pressure of a gas raised from RT to 250 is that air is basically an ideal gas in this temperature and pressure range, and air mixed with steam share about the same temperature at 15 psi, therefore any admixture at this pressure (which is what the wobble weight ensures is constant) will still be 250 degrees.

It is actually the fact that the air is heated by steam that is irrelevant. If you had 10% air in your cooker still (which you wouldn't by the time you've reached pressure plus 5 minutes), the temperature would still be about exactly 250 degrees when the pressure inside the cooker is 15 psi. What heats the air is not important. It's the temperature of the air that matters -- both for the pressure and for the sterilization. Can we agree that the air and the steam in the PC are the same temperature?

All of that is almost certainly overthinking this, though. A cc of water becomes about a cubic meter of steam at STP (which the steam is escaping to). That steam displaces the air in the PC in a logarithmic fashion. In just a few minutes there is essentially zero air in the cooker. And if you reduce the heat under the cooker until a very light stream of steam escapes, those three quarts of water will still last at least 10 hours.

I agree with you on this though, a fancy autoclave is easier and more automatic than a PC. I'm not disrespecting you, just disagreeing. Honestly, those extra 2.5 psi are probably not going to blow out the safety plug. I just wouldn't do it.


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Offlinein_dot
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: phatty]
    #24684904 - 10/04/17 10:54 PM (5 years, 5 months ago)

The air and the steam in the PC will never be the same.  They have different heat capacities.  Regardless if you act as though they are ideal, the specific heats will differ, meaning that, unless it was a closed and isolated system, an equilibrium of temperature can't be achieved.  It's nowhere near closed as my kitchen warms a degree or more just from PCing something for a couple hours so there's loads of energy being released from the system.  As such, the compound with the lower heat capacities will always be a slightly higher temperature. As it will rise in temperature more per unit of energy absorbed. 

It's too dynamic of a system for us to assume they'll be the same temperature.

Now whether the differences in those temperatures would be significant enough to drop it below the preferred 250 degrees, I don't know.  But I just go ahead and vent for at least 10 minutes so I don't have to wonder if it's an issue or not. 


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Edited by in_dot (10/04/17 10:55 PM)


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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: in_dot]
    #24684936 - 10/04/17 11:21 PM (5 years, 5 months ago)

Air and the steam are the same temp. But if theres any air in there it literally cant hit 250 at 15 psi. It would be less than 250 at 15 psi of theres any entrapped gas.
Steam has way more energy and releases it as it condenses on your media air doesn't sterilize in the PC steam does.

Quote:


. If you had 10% air in your cooker still (which you wouldn't by the time you've reached pressure plus 5 minutes




Wrong

B


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Invisiblephatty
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: in_dot]
    #24684939 - 10/04/17 11:23 PM (5 years, 5 months ago)

Cool, Bro. I personally doubt any of it makes any difference though.

Heat capacity doesn't affect anything because the gases mix molecule-by-molecule. The temperature of both species will be exactly the same at steady state, and almost exactly the same during the heating up period because the viscosity of gases is so low that we can assume perfect mixing.

The mixture is treated as a single species with a blended "average" of the physical properties of the two (or actually the many species that are in air and steam combined, since air is itself a mixture of gases). That mixture has a heat capacity somewhere between that of air and steam.

That heat capacity (specific heat) of air you mention is actually the composition-weighted average of the heat capacities of the various gases that comprise air, which we treat as perfectly mixed, and as a single species.

The heat capacity reflects how long it takes at a given heat (flame) to reach the steady state temperature, but doesn't at all affect that temperature.

I have no idea what the temperature of the kitchen has to do with any of it, unless you are addressing my approximation of the volume of steam escaping to STP outside the PC...

Fun conversation. I still think you are the bomb (not referring to the PC :smile: and thank you for all of your shared expertise.


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Offlinein_dot
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: phatty]
    #24684951 - 10/04/17 11:32 PM (5 years, 5 months ago)

I was assuming they were in a pure, separated compound setting just cause we were already making the assumption they are behaving ideally (even though they aren't).

And just mentioned the kitchen to demonstrate it's neither a closed or isolated system so a lot of the assumptions are rather far fetched

But yes I agree if we assume perfect mixing, they will be the same

I use the quarters on top cause it's quieter, and I guess it also doubles as making it a more closed, stable system albeit a bit more dangerous if you're an idiot:awedance:


Edited by in_dot (10/04/17 11:41 PM)


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Invisiblephatty
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: bodhisatta]
    #24684984 - 10/05/17 12:11 AM (5 years, 5 months ago)

Quote:

bodhisatta said:
Air and the steam are the same temp. But if theres any air in there it literally cant hit 250 at 15 psi. It would be less than 250 at 15 psi of theres any entrapped gas.
Steam has way more energy and releases it as it condenses on your media air doesn't sterilize in the PC steam does.




Wrong, and wrong. If air is 250 at 15 psi, and steam is 250 at 15 psi, then admixture of any proportion is 250 at 15 psi.

Steam does have more energy per volume than air at the same temperature. But it is temperature that equalizes over time, and it is temperature, not steam, that sterilizes. I think what you are observing is that steam transfers that heat more rapidly than air does to a medium cool enough to condense the steam. Absolutely concur. But the temperature can actually exceed 250 F if there is air in it...

Dude: Atmospheric pressure is 14.7 psi absolute. Raising the pressure to 15 psi guage (29.7 psi absolute) doubles the pressure. The absolute temperature also doubles, then. From 298 K to 596 K -- which is actually hotter than the steam at that pressure. Okay, so it's not *exactly* twice the pressure, it's 1.98 times the pressure. So the temperature of air at that pressure is only 590 K (or 318 degrees F). So you're actually *better off* with some air in there.

It may or may not take some more time to reach steady state due to the difference in heat transfer rates -- due to both of the phenomena you talked about, the difference in heat capacity and the lack of condensation for the partial pressure of air. (Those are working against you as you heat the steam, though). At any rate, the air is not going to hurt you when it comes to reaching sterilization temperature. Just take your time.


Edited by phatty (10/05/17 12:22 AM)


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Invisiblephatty
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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: in_dot]
    #24684992 - 10/05/17 12:21 AM (5 years, 5 months ago)

Okay, actually, you're right. All of the other arguments assume adiabatic conditions, which isn't even close to real (we're heating the pot). Truth is, everything inside that pot is at the same temperature -- the temperature of the water-to-water-vapor interface at 15 PSI, which is 250 F. Period. Can't escape physics and thermodynamics, can you. I'm just saying if anything, the air would be at a higher temp if compressed adiabatically to 15 PSI than steam.


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Re: Bod's Easy AF how to use your pressure cooker for mycology TEK [Re: phatty]
    #24685010 - 10/05/17 12:35 AM (5 years, 5 months ago)

Ill get back to you tomorrow or Friday with a better reply.

If theres entrapped air and the gauge reads 15psi an internal thermometer will read less than 250F

Steam carries more "latent heat" energy. It transfers more energy.

There's steam jacketed kettles not hot air jacketed kettles.

Steam carries more energy than the water hence the first layer of jars needing to be at least 50% exposed to steam.


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