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OfflineGalaxytripper
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Sterilization technique:pressure cooker vs. canner
    #21837572 - 06/21/15 03:27 PM (8 years, 7 months ago)

Dear Shroomerites,
I had a couple of intial failed PF teks a good while ago,doubtless because of dumbass newbie mistakes.

The first time, I put the jars into the PC for 75 minutes (and btw, the PC has no gauge, just 2 settings, "low" and "high" pressure). I used tape over the 4 holes, plus a layer of tin foil as prescribed.
I know the idea of the tin foil is to stop water dripping onto the lids. But that's the least of your worries with a pressure cooker, since the pressure blew off many of the lids, and ruined the water balance. I went ahead anyway, but sludge and contams were my just reward.

Next time, I decided to use SFDs, plus parafilm around the jar lid rims before cooking, plus I held the tin foil down tight with rubber bands. That will stop my lids blowing off, I thought. Well it didn't.

These attempts occurred before I happened on the instruction to only put enough only water in to barely cover the bottom of the
jars, mistake discovered too late. Anyway, after a long break,I'm trying again today, so:

If you're using a PC (even though the precise pressure is unknown) how, -by any stretch of the imagination, would the pressure NOT force itself under the tin foil and into the substrate to ruin it, even if you are using tape over the holes? Esp. if the tin foil is not sealed down in any way, and we're talking about high pressure (whatever that is).

If the scenario that I posit is a given(or if not, pls. explain) how could the loose tin foil method work, even in principle? Can someone explain?
Wouldn't I be better off using my big canner to boil the jars for maybe 90 min. to prevent these catastrophes? If I just straight boil, for how long?

What am I doing wrong? What is the error of my ways?


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Offlinematsc
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Re: Sterilization technique:pressure cooker vs. canner [Re: Galaxytripper]
    #21837619 - 06/21/15 03:38 PM (8 years, 7 months ago)

Even in a PC, the foil is simply to avoid drips. No need for it to be tight or anything, just covering the tops.

If your lids are being blown off, its from the pressure dropping too quickly after cooking. This leads to rapid production of steam within the jar and pressure build up.

I take it that you are doing something after the sterilization, either pouring water on the PC, opening a valve, pulling off the jiggler, something along those lines. Dont. Once your time is up, just kill the heat and let the whole system come to room temp as slow as it wants. Give it a few hours. You should be able to touch the lid with bare hands before you even consider opening it.

Also, by "tape" are you referring to a cloth/milipore tape?


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OfflineGalaxytripper
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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21837650 - 06/21/15 03:48 PM (8 years, 7 months ago)

Hi Mattsc,
Thanks for taking this, and yes, you hit the nail on the head. After the PC says my 75 mins. are up, I did take a utensil and let the steam out of the jiggler.

Although how  "pressure dropping too quickly after cooking leads to rapid production of steam within the jar and pressure build up, is not making sense to me. The steam (pressure) would be there anyway, right?


'Also, by "tape" are you referring to a cloth/milipore tape? '

I'm referring to parafilm, bought from a scientific supplier, which is plastic in nature. That melted nastily too.


Edited by Galaxytripper (06/21/15 03:52 PM)


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Re: Sterilization technique:pressure cooker vs. canner [Re: Galaxytripper]
    #21837687 - 06/21/15 03:57 PM (8 years, 7 months ago)

Ok, quick lesson in thermodynamics and PC operation.

When you put the PC on the heat, the water inside begins to turn to steam. As the steam builds up and displaces the air, you either close a valve or put on a weight or something. Now you have a sealed vessel filled with water vapor. As you continue to heat up, this vapor builds up, and increases the pressure in the vessel.

The boiling point of water is a function of pressure. At sea level (what we would call 0 PSI), this is about 212F or 100C. As you ramp up the pressure, water will stay liquid at higher temperatures. At 15PSI (roughly +1 atm or double what we experience at sea level) its about 121C.

What this means is the water in your PC is still liquid, even though it is far above the "normal" boiling point of water. So if you suddenly drop the pressure, that water is now waaay above its boiling point, and with no pressure to keep it liquid, it will all instantly go to gas phase and violently boil away. By letting the pressure off slowly, along with a corresponding temperature drop, the water will stay more or less in its liquid phase all the way down to below its normal boiling point.

Also, if you are doing the traditional PF Tek, no need to tape the holes. The vermiculite layer over the top will act as a barrier (so long as you dont move or wiggle or mess with the jars). If you really want to tape over them for peace of mind, hit up a first aid section of a local grocery store and buy a roll of micropore paper tape. Its not a perfect filter material, but its better than nothing. (But again, the vermiculite layer is the real barrier here, and the tape just acts as a buffer in case you like messing with your jars too much as they colonize)


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Edited by matsc (06/21/15 03:58 PM)


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OfflineGalaxytripper
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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21837827 - 06/21/15 04:30 PM (8 years, 7 months ago)

Ok, thanks for the great thermodynamics tutorial, mattsc.

On the point about the tape: I'm confused now about the context for the tape on the lids. My understanding was that (contrary to some information out there) you don't need tape on the lid holes for the context of colonization. Sure, after you've sterilized and inoculated, you can leave the holes open. This I get.

And, wouldn't the tape surely be for the sterilization phase, if anything, in order to create a watertight barrier, while steaming/boiling, yeah? Or if not, why is there a conversation about tape at all?

Or is there any confusion of context here on my part?


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Re: Sterilization technique:pressure cooker vs. canner [Re: Galaxytripper]
    #21837863 - 06/21/15 04:42 PM (8 years, 7 months ago)

Micropore tape is used by some as a means of keeping contaminants out of the jars. I use it myself on my grain jars when growing oyster and shiitake spawn. I also use filter disks between the lid and the ring, but the tape acts as a barrier under the disk so there is something to keep crap out and that I can stick a syringe needle through for inoculation. It restricts gas exchange somewhat, but I'm too lazy to make proper filter lids with healing injection ports, and my normal method works fine 95%+ of the time.



But with PF tek cakes, there is really no need (again, other than peace of mind). During sterilization you want steam to get in, it is what transfers heat and will kill anything in there. You use foil to keep drips and bulk water out, but steam should be able to come and go as it pleases. After sterilization the vermiculite layer is what keeps things clean inside.


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Edited by matsc (06/21/15 05:07 PM)


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OfflineGalaxytripper
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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21838058 - 06/21/15 05:27 PM (8 years, 7 months ago)

Thanks for that,mattsc,

Lastly, not to drag this out:

"I also use filter disks between the lid and the ring".

Q. If the filter disk goes in the middle, in that case, how can you locate the holes to inoculate??

Q. You would stick a syringe needle through the disk for inoculation.

I thought you would pull up the tape off each hole, inject, then replace the tape, rather than put a hole in it. Why wouldn't you do that?


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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21838105 - 06/21/15 05:36 PM (8 years, 7 months ago)

I put a filter disk between the ring and lid, but pull it off when I'm injecting. When inoculating, I pull the ring and disk (very carefully ensuring the lid itself stays in place), inject through the taped holes, put a new piece of tape over the hole I just made (which you can see in my picture), then replace the disk and ring.

With PF tek style jars its slightly different, but the main theme stays the same. Poke down through  the vermiculite layer into the substrate, then pull the needle back up so the vermiculite settles back in and "seals" the hole you made. You can also paper tape over the holes if you like, but its not necessary if you keep a steady hand and can leave the jars alone.

The whole set up is for redundancy. The filter disk is the main method of keeping things clean, but I keep the paper tape there as a minor back up for when I pull the disk to inject (or if my disk ends up with a tiny hole or something along those lines). I put the paper tape on before I PC the jars. Its gas permeable so steam can move in/out, but the high heat sort of melts it onto the lid so pulling it would be a pain. Its easier to just poke through and tape over. With PF jars you probably would be better off taping AFTER injection, if you want to use tape at all.


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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21838149 - 06/21/15 05:45 PM (8 years, 7 months ago)

no need for filter discs for pf-tek. just use dry verm on top and keep the cakes still until they're done!
4 open holes in the top is fine, you can re-apply micro pore tape if you wanna be even safer. but keeping the dry verm dry and in place is key!
and a "clean" enough spore syringe of course!


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Re: Sterilization technique:pressure cooker vs. canner [Re: matsc]
    #21838207 - 06/21/15 05:59 PM (8 years, 7 months ago)

Thanks mattsc, for the clear explanations. Great job.


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Re: Sterilization technique:pressure cooker vs. canner [Re: spacechildo]
    #21838212 - 06/21/15 06:00 PM (8 years, 7 months ago)

Thanks for the info.


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Re: Sterilization technique:pressure cooker vs. canner [Re: Galaxytripper]
    #21838611 - 06/21/15 07:28 PM (8 years, 7 months ago)

Yeah it needs to be micropore tape if you use tape. Otherwise air can't pass through it and there'll be a difference in pressure. I'd never imagine it could lead popping the whole lid off but it can pop the tape off at least or leave a vacuum in the jar afterward.


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Re: Sterilization technique:pressure cooker vs. canner [Re: Kizzle]
    #21838750 - 06/21/15 07:47 PM (8 years, 7 months ago)

Yeah, thanks for the info.


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Re: Sterilization technique:pressure cooker vs. canner [Re: Kizzle]
    #21873687 - 06/29/15 01:40 PM (8 years, 6 months ago)

Yeah, thanks Kizzle.
What blew the lids off was incorrectly using my cheapo pressure cooker, apparently. After the boil, I let the steam out manually, which caused some pressure differential, explained earlier(by Hyphae)by reason of physics which is slightly above my head and pay grade.


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