Home Brew Myths - Part 2

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MAH

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OK this one crops up on US sites quite often, and that is you can't use plastic for long term storage of beer because air will diffuse through the walls and your beer will suffer from oxidisation. A recent posting on HBD suggested that plastic shouldn't even be used for long term lagering (I'm pressuming they mean maybe 6-8 weeks).

In Australia most of us use plastic for our fermenters and even CCing/lagering, so what is the collective wisdom on this. Is it true or is it a myth. Does anyone have any hard data on the amount of air that diffuses across a plastic fermenter wall, and how much oxygen actually makes its way into the beer? Just an assumption, but I would think that your beer gets exposed to more oxygen during racking.

Thoughts?

Cheers
MAH
 

warrenlw63

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Think that myth goes way back to the early 1980's when Charlie Papazian was the "guru" of gurus in his flares bodyshirts and long sideys sipping on a pint while stirring his magic ingredients in a ... drumroll 'GLASS CARBOY' :lol:

Those pics in The Complete Joy of Home Brewing still make me ROTFLMAO! Polyester rocks! :D

I particularly like the pic of him and his S/O bottling. She's leaning her hairy armpit over the bottling bucket holding the racking cane while he bottles. Funny part is the bottling bucket has no lid. That would have wound up one wafty beer. :blink:

Warren -
 

Tony M

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A mate uses PET bottles for his quaffers but finds the beer degrades after about a year. Long term stuff he puts in brown bottles.
Even though the bottles are clear, I dont think it's UV damage as that can happen in a few minutes.
 

AndrewQLD

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I have always found this idea to be suspicious, I would have thought you would need less pressure in the fermenter than the outside air pressure in order for the beer to pull the air through the plastic???

and as far as PET bottles go, with all the pressure in them form the gassing I can't see how any air could get in. If anything would'nt the CO2 be trying to seep out of the bottle???

Just my dunb thought for the day

Andrew
 

Boots

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But for fermenters which is what the first post was about ...

Sosman's link gives us the figures below for HDPE (i assume fermenters are HDPE?? don't have one with me at work):

<snip>
Plastic material Oxygen permeability with 25 m thickness

(cm3/m2 24h bar)

Low density polyethylene (LDPE) 7000-8000
High density polyethylene (HDPE) 2800-3000
<endsnip>

Anyone know enought to translate these figures for us less smart people, so that they relate to the everyday fermenter / plastic carboy / CC'ing cube?

By the way PET in comparison has a rating of 45 -90. is this better or worse?
 

Boots

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This link supports AndrewQLD's theory about CO2 exiting under pressure as a bigger problem than Air getting into a PET bottle.

Has more info on all types of plastic as well if anyone can interpret

Another Link

I guess this might work in the same way, although to a lesser extent, for fermenters CC cubes??
 

sosman

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To be honest, putting this in context, I have no qualms about fermenting my beer in the old HDPE fermenter.

I am no chemist but I understand gasses work according to partial pressures. Ie, even though there is CO2 under pressure in your bottle, if there is no oxygen in there, then atmospheric O2 will seep in.

Maybe someone who actually knows about this stuff can post.
 

sosman

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Boots said:
But for fermenters which is what the first post was about ...
Hmmm, I went back and re-read the first post and it mentioned something about "long term storage" - I don't believe that precludes bottling beer in PET.
 

Boots

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Sosman, i was looking at the second paragraph where the question was posed:

Does anyone have any hard data on the amount of air that diffuses across a plastic fermenter wall, and how much oxygen actually makes its way into the beer?
But do agree that it's just as relevant for PET as so many people use PET bottles, and some competitions enforce the use of PET ...

I also think I'll wait till someone knows what they're talking about contributes :rolleyes:

Cheers
 

chiller

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On PET bottles.

I stipulate PET bottles for the Mash Paddle for consitency and safety.

The beer in the first paddle was a low alcohol job and showed no ill effects from travelling and storage. The bottles all held good carbonation. There were no wet cardboard or sherry flavours indicating oxygen problems.

If you make a beer that you intend to drink within 4 - 5 months you should be fine.

I sadly only have 2 bottles [glass] left of a Rochefort clone four of us made 15 months ago. It is fresh and very Belgian. For anything long term -- go glass.

The worst oxygen problems I've had have been with glass carboys. The rubber bung decided to lose it's grip and just sit in the neck of the carboy but not fully sealed and I didn't realise.

Steve
 

MAH

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OK, it seems that so far none of us actually know how much oxygen diffuses across a platic fermenter wall. I'm guessing that this one might be a case of lots of people repeating what one person said. That one person was probably quite anal and wanted to eliminate the 0.05% chance of beer spoling due to oxidisation from using plastic. It seems to me a bit like the fear over using brass ball valves etc, they aren't perfect so they get a bad reputation, even though you probably need an industrial lab to detect any difference in the beer (I'm not going to even mention Chiller and his Alzheimer causing brewery - oops I did mention it ;) ).

Lets keep searching for some more solid answers.

Cheers
MAH
 

kungy

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Boots said:
Plastic material Oxygen permeability with 25 m thickness

(cm3/m2 24h bar)

Low density polyethylene (LDPE) 7000-8000
High density polyethylene (HDPE) 2800-3000
I have a comment as to whether plastic fermenters are air permeable etc. I'm not discrediting the evidence just interpreting the evidence. The specs taken from sosman refers to 25 micrometres, therefore if 1 micrometer equals 0.001 millimetre, the specs taken refer to a 0.025 millimetre thick test sample. For our fermenters the plastic is considerably thicker, say 3 millimetres.

Therefore whilst the specs are accurate for a test sample of 25 m, fermenters are a different story altogether as they are thicker. Therefore for me, ferementers aren't a problem if the permability is relatively low, due to the thickness of the plastic ferementers compensating

Cheers

Will

PS Feel free to pick my logic apart
 

chiller

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kungy1 said:
Boots said:
Plastic material Oxygen permeability with 25 m thickness

(cm3/m2 24h bar)

Low density polyethylene (LDPE) 7000-8000
High density polyethylene (HDPE) 2800-3000
I have a comment as to whether plastic fermenters are air permeable etc. I'm not discrediting the evidence just interpreting the evidence. The specs taken from sosman refers to 25 micrometres, therefore if 1 micrometer equals 0.001 millimetre, the specs taken refer to a 0.025 millimetre thick test sample. For our fermenters the plastic is considerably thicker, say 3 millimetres.

Therefore whilst the specs are accurate for a test sample of 25 m, fermenters are a different story altogether as they are thicker. Therefore for me, ferementers aren't a problem if the permability is relatively low, due to the thickness of the plastic ferementers compensating

Cheers

Will

PS Feel free to pick my logic apart
Very good logical post.

And I think MAH said something about Aluminium but hey I can't remember. :chug:



Steve
 

Bobby

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Therefore for me, ferementers aren't a problem if the permability is relatively low, due to the thickness of the plastic ferementers compensating
Has anyone ever noticed any problem with plastic fermenters?? I think most of us use them here anyway.
Where/what is the problem with permeability if no one has noticed any difference to there beers?

:unsure: I just woke up so i doubt i have articulated what i mean so i will editi it later.... :unsure:
 

Chatty

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Nice post kungy - couldn't agree more :D

Chatty
 

Backlane Brewery

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Thanks to Kungy1 for translating micrometers into the real world...does someone want to measure the thickness of an actual plastic fermenter to get a definitive thickness?
We now brew in glass, cos it looks nicer. We secondary in plastic, cos we only have one 25l glass demijohn. We bottle in glass, cos you have to buy PET bottles, and we think they look, well, tacky.
As with Bobby's post, we never noticed any problems when we were brewing in plastic. If we were CCing in plastic for weeks or storing PET bottles for months, who knows?
Another area where HB comes down to personal choices & finances.
 

Darren

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Howdy,
I always thought the real problem with plastic is that it scratches very easily, especially when cleaning stuck on, dried up crud!
Deep scratches can be great places for bugs to hide in.

Gas transfer across a membrane will occur if the membrane is porous, especially if the fluid is in direct contact with the membrane.
Now there is nothing wrong with storing beer in plastic for a couple of weeks. I expect though, that extended lagering of a dopplebock or similar in plastic for 3 or more months could be a problem.
cheers
Darren
 
J

Jovial_Monk

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I use bleach to clean crud or at least soften it up to the stage it can simply be wiped off, no scratches.

I have lagered a spiced lager and a doppelbock for 4 and 5 months respectively in plastic 'cubes' the spiced lager is now 3 years old and has no carboady or other staling/oxidative flavors.

I have also aged an IPA and a RIS for 12 months--in steel corny kegs! i reckon up to 6 months in plastic is OK

Jovial Monk
 

MAH

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Jovial_Monk said:
i reckon up to 6 months in plastic is OK
Well Mr Monk, once again you seem to have missed the point. This thread is about possibly debunking a few homebrew myths, therefore we're after some hard and fast data. Others have taken the time to provide some evidence on the permeability of HDPE and others have had a crack at interpreting the data. You've just tossed up pure speculation.

However in a weird way you've added to the theory that a lot of homebrew "knowledge" is just myth and hearsay. Even supposedly well versed HBS owners will peddle what they "reckon" as brewing facts.

Let's try and get some evidence based practice back into homebrewing.

Cheers
MAH
 
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