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Offlinetradergordo
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Registered: 07/18/08
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All American Sterilizer (pressure cooker) - why vent?
    #9350838 - 12/02/08 11:51 AM (15 years, 3 months ago)

Im just curious - I think the instruction manual and most directions I've read say you should put the pressure relief toggle valve in the up position and let the unit vent (visible steam coming out for at least 5 minutes) before closing the valve and letting pressure build.  Im just curious to know why this is required or recommended?  (Note that I am NOT talking about models with a weight type pressure regulator - those obviously do not require special initial venting because they vent on their own as pressure builds, I have the 25x model, electric, with pressure toggle valve).

I tried searching this forum, but didnt find a definitive answer.  I think the ideas are that it purges the unit of its original and unclean air, or it is somehow needed to make the pressure gauge function properly (which doesnt make much sense to me).  If you didnt purge the original air, wouldnt it still be sterile after the heat/pressure cycle was over? 

The only reason I ask is that I have the electric model which is a pain in the butt, it takes almost an hour (maybe 45 mins) to reach 15 PSI when you start with room temp water, I dont want to babysit the thing every time I use it, I just want to set a timer and go away.  If I have to do the purge, that means I cant just set a timer and go away, I have to come back in X minutes, verify that I can see steam coming out, wait another 5 minutes, close valve, then set timer and go away.  This becomes a pain when you are trying to use it a lot (several times a week) - especially when you want to turn it on before leaving for work in the morning, or before going to bed at night. 

So I was just curious to know if it really is necessary to do this venting step, and if there are others that have ignored this and what are your results like?

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Invisiblesandman420
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: tradergordo]
    #9350960 - 12/02/08 12:12 PM (15 years, 3 months ago)

The reason to vent on toggle valves is to fill the vessel with steamed air before it builds pressure. Im no physicist or anything but I think that with the unit sealed before steam is made, there isnt enough room for the steam to fill up the vessel since its already full of air. I wouldn't skip this step personally but you may try a cycle without doing it just to see for yourself.


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Invisibledurban_poison
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: tradergordo]
    #9352140 - 12/02/08 04:15 PM (15 years, 3 months ago)

its simple really, when you heat gas the molecules move faster and are farther apart. therefore the cooker has less air in it which helps the toggle provide a better vaccum after cooling. this vaccum allows you to not have to empty the cooker immediatly after sterilizing.

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InvisibleFooMan
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: tradergordo]
    #9352185 - 12/02/08 04:24 PM (15 years, 3 months ago)

I've always heard it gets the pockets of air out of your PC. You're supposed to do it regardless if you're using a weight or toggle valve.


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Invisibledurban_poison
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: FooMan]
    #9352608 - 12/02/08 05:37 PM (15 years, 3 months ago)

pockets of air? where and how would there be pockets of air in there? i understand why it helps the vaccum but air pockets?

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Offlinefukuyama
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Registered: 11/22/08
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: durban_poison]
    #9352764 - 12/02/08 05:58 PM (15 years, 3 months ago)

Air has nothing to do with it. As soon as that puppy gets up to a boil and steam starts coming out almost all of the air has already been forced out of the cooker.

The reason why you wait till its steaming is so you can accurately time what your cooking (or in this case sterilizing)... so you don't over or undercook.

"Purging" or whatever helps give the contents of the jars (or whatever your trying to cook) time to reach equilibrium with the temp of the steam.

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InvisibleFooMan
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: fukuyama]
    #9354282 - 12/02/08 08:53 PM (15 years, 3 months ago)

Quote:

durban_poison said:
pockets of air? where and how would there be pockets of air in there? i understand why it helps the vaccum but air pockets?




According to hyphae, it's "dry" pockets, so maybe my wording was a bit off on what I heard:

http://www.shroomery.org/forums/showflat.php/Number/5335979#Post5335979

Instead of just guessing, I decided to do a quick google search.

Here are a few things I pulled up (thanks google):

Quote:

If you are using a pressure cooker with any type of weighted pressure regulator remember to remove the weight while the cooker is in the process of heating up. When you see a steady stream of venting steam, then replace the weight on the vent tube. This will exhaust all the air and create a live-steam environment inside the pressure cooker, which means food will cook faster because steam is hotter and more penetrating than air.




From: http://missvickie.com/library/whistling.htm

Another find regarding sterilizing microbial media:

Quote:

After the cooker is loaded, turn on heat with the exhaust valves open, so that air can escape, when pure steam is coming out, close the exhaust valve. If air remains inside the cooker, proper sterilization temperatures will not be reached




From: http://www.disknet.com/indiana_biolab/b024.htm

Quote:

fukuyama said:
Air has nothing to do with it. As soon as that puppy gets up to a boil and steam starts coming out almost all of the air has already been forced out of the cooker.





So, it seems air does have something to do with it. :shocked: :peace:


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OfflineDigital Reality
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: FooMan]
    #9354452 - 12/02/08 09:14 PM (15 years, 3 months ago)

lol nice... thats pretty much priceless :smile:

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Offlinetradergordo
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: FooMan]
    #9354516 - 12/02/08 09:21 PM (15 years, 3 months ago)

Thanks a lot guys, I guess its that "live-steam environment" that really is important.  Which unfortunately still leaves a bit of a dilemma, it just seems like after all these years, there SHOULD be a simple set it and forget it sterilizer that doesn't require all this babysitting.  Don't want to sound like I'm whining, but the X25 costs over $500 bucks, for that kind of money you'd think someone could do better - like a digital countdown timer that only begins to count down when the unit hits 15 PSI, and a self venting feature so you don't need to interact at all in the process.

I'm sure something like that exists and it costs 10 grand, haha  :smile:

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Invisiblesandman420
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: tradergordo]
    #9354793 - 12/02/08 10:01 PM (15 years, 3 months ago)

Yea they are called autoclaves! They work off of a boiler which is all automated.


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- Sandbag Tek - How To Sterilize Spawn Bags - All About Static Pressure / Pressure Drop for DIY Flow Hoods - Sandman's LC Tek-

Marijuanaut escapes earth to cultivate - Grow-room is church temple of the new stoner breed

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Offlinetradergordo
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: sandman420]
    #9357152 - 12/03/08 10:48 AM (15 years, 3 months ago)

Technically the All American sterilizers ARE "autoclaves", they just aren't fully automatic.  There are auto and manual autoclaves, AA only makes manual as far as I know.  There are 16 automatics listed on ebay right now, and the cheapest is a very used looking, $1500 dental unit.  New ones are over $2,000 and most don't seem any bigger than the all american 25 quart.

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OfflineRogerRabbitM
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: sandman420]
    #9357332 - 12/03/08 11:33 AM (15 years, 3 months ago)

Water expands when it heats.  Therefore, if your toggle valve is closed, you might build pressure, but it's air pressure, not steam.  Always allow the unit to vent steam for several minutes.  The idea is to heat the surface of the cooker and the jars within, prior to closing the valve to build steam pressure.  This assures that your pressure is actually steam, not air.
RR


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Invisibleshroomophile
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Re: All American Sterilizer (pressure cooker) - why vent? [Re: RogerRabbit]
    #9358450 - 12/03/08 02:01 PM (15 years, 3 months ago)

Air is a poor conductor of heat;however,water is a good conductor.


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