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OfflineWaldfried
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Pre-sealing 0.2 micron filter bags - Let's settle this once and for all
    #21994423 - 07/25/15 09:45 AM (8 years, 6 months ago)

Greetings, my fellow Shroomerites!

I'm am really curious about the method of sealing rye bags prior to sterilisation. In my case, pre-sealing would cut down redundant work time as well as contamination risks so I'd like to make it my standard procedure for spawn preparation.
In my case my pressure cooker handles a single large unicorn bag filled with approx. 4,5 litres of rye.

The issue I'd like to discuss here is the manufacturer's suggested pore size of 5 micron when taking the route of pre-sealing.

  • In my understanding, pore sizes of 5 micron (bag type 3B) are too large and pose a threat to possible contaminations as mold spores can be as small as 1,5 micron.

  • On the other hand, 0.2 micron filters (bag type 3T) offer an insufficient air flow rate to prevent the bag from exploding/rupturing during the cooldown.


To clarify what happens inside a pressure cooker during sterilization i feel free to quote RR:


Quote:

RogerRabbit said:
The pressure inside the bag and outside will not be the same except during the half hour or so that the PC and the bags are at full temperature.  During the ramp up to 15 psi, pressure in the cooker rises faster than pressure inside the bag, and then during cool-down, pressure leaves the pressure cooker faster than the bag can cool and release its pressure.  The result is inflated and/or burst bags.
RR




.

The issues open for discussion are as follows:
1. How to prevent the bag from rupturing/exploding?
2. How does pressure affect the PTFE filter membrane pore size?


I'll leave a link to the Product Catalogue for technical reference only, no advertising intended.
The manufacturer of the PTFE membranes I use for jars provides data for their 0.2 micron membranes which I assume is similar to the PTFE membranes used for the bags.
They specify the air flow rate for their 0.2 micron membranes with 0,2 litres / min / cm² / 0,05 bar. May come in useful.



I invite everybody with good ideas, first-hand knowledge and experience to join this discussion to settle this issue once and for all. Many have asked wheter it is possible, but the answers are often unclear or contradicting. Let's gather all the infos and make this a beacon for future reference!

Namaste.



Quote:

People who say it cannot be done should not interrupt those who are doing it.




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InvisibleJuiceh
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Waldfried]
    #21994458 - 07/25/15 09:55 AM (8 years, 6 months ago)

Trich spores are .3 micron.

I once presealed a couple .2 micron bags. Bad idea. Don't even bother. I had a 5lb weight sitting on top of the bags. The bags inflated and pushed the weight off to the side as they expanded and then burst. This was done in an AA921 and the only thing that prevented the bags from blocking the exhaust ports was the 2nd caning rack I had put on top of the bags and weight.

At the time I did not know what pore sizes the bags were. They had come from a vendor prefilled with substrate that I got as a gift. If I recall I think the substrate was pasteurized and the bags were presealed. For some reason I thought the vendor used the slightly cheaper 5 micron bags and that I could preseal and PC them. I later contacted the vendor to find out that they were in fact .2 micron bags.

I did try a second time with a smaller bag, I wrapped it with zip ties to try to prevent it from expanding. It just blew out the side.

Don't waste your time and endanger yourself or anyone else in your home by doing this.

A tyvek sleeve in the neck of a .2 micron bag works great. If you inoculate in front of a flow hood or in a SAB and your sterile technique doesn't suck your contam rates should be low. Sealing after the g2g transfer into the bag allows me to get a nice plenum of clean hepa filtered air in the bag. I don't have to hang a presealed bag from something so that the bags self inflate over time. My contam rates are sub 1% using this method. The only times I've actually lost bags I was in a rush and accidentally let the opening of the bag get outside of the flow of air from the hood.


Edited by Juiceh (07/25/15 10:15 AM)


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InvisiblePastywhyteMDiscord
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Juiceh]
    #21994479 - 07/25/15 10:00 AM (8 years, 6 months ago)

I even managed to burst a 0.5 micron presealed bag once.


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Invisible36fuckin5
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Pastywhyte]
    #21994759 - 07/25/15 11:18 AM (8 years, 6 months ago)

I've blown out many bags trying to preseal them. It just doesn't work. The 5 micron bags let in contams. It's as simple as that.


--------------------
Redd Foxx said:
If you're offended I don't give a shit and don't come see me no more.

Pat The Bunny said:
A punk rock song won't ever change the world, but I can tell you about a couple that changed me.

bodhisatta said:
i recommend common sense and figuring it out.

These are the TEKs I use. They're all as cheap and easy as possible, just like your mom.


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InvisiblePastywhyteMDiscord
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: 36fuckin5]
    #21994787 - 07/25/15 11:26 AM (8 years, 6 months ago)

0.5 micron bags can work but you have to keep the sporeload on the filter down.


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Invisiblemaddchef
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Pastywhyte]
    #21994917 - 07/25/15 12:00 PM (8 years, 6 months ago)

You CAN preseal 0.2um bags but to be successful you must pretty much get all the air out to begin with and once the cycle is over you have to lower the heat in steps over the course of about 2 hours.

No one wants should have a pc cycle last that goddamn long and be that goddamn tedious.

The bursting happens on cooldown. The airspace in the pot cools before the thermal mass of the bag. The bag inflates to create equilibrium and thus pops as the filter cannot keep up.


--------------------
In the land of the blind, the one eyed man is king.

All mushrooms are edible, but some only once.....                     

                                        Easier than cakes

I do science and shit.

:havesomescience:


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OfflineWaldfried
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Pastywhyte]
    #21995006 - 07/25/15 12:20 PM (8 years, 6 months ago)

And what if we could reduce that airspace to a minimum to prevent it from inflating completely in the first place? Provided there is enough space left for the steam to move around. I remember someone saying somewhat similar in another post...
The bag's inflation would be obstructed by the PC itself (or some custom-made rack maybe), making a faster cooldown possible...
Or am I missing some essential details here?
Any empirical data on filter membrane behaviour under pressured airflow?


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InvisibleJuiceh
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Waldfried]
    #21995072 - 07/25/15 12:35 PM (8 years, 6 months ago)

I tried to get all the air I could out of the bags. They still popped. I put stuff on top of the bags to try to prevent them from expanding. They still popped. If you built a custom rack to hold the bags in place so they couldn't unfold and expand, the sides would blow out wherever the weakest point is. It's not worth the effort trying to figure out a way to do it. If there's a way, it probably would be way too much of a pain in the dick to do or we'd already know how and be doing it.


--------------------
Trade List

How I make 15 lbs of casing in a 941. How I line 12 shoeboxes with 1 39gal bag. How I Deep Fry Cubes!
RogerRabbit said:You need a bigger pressure cooker for this hobby. RR


Edited by Juiceh (07/25/15 12:36 PM)


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Invisible36fuckin5
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Re: Pre-sealing 0.2 micron filter bags - Let's settle this once and for all [Re: Juiceh]
    #21995095 - 07/25/15 12:39 PM (8 years, 6 months ago)

:whathesaid:

We don't make extra work for ourselves cause we want to.


--------------------
Redd Foxx said:
If you're offended I don't give a shit and don't come see me no more.

Pat The Bunny said:
A punk rock song won't ever change the world, but I can tell you about a couple that changed me.

bodhisatta said:
i recommend common sense and figuring it out.

These are the TEKs I use. They're all as cheap and easy as possible, just like your mom.


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