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brazedowl 12-13-2011 05:01 PM

Hard Data...
 
So I've heard all kinds of stories about what to use for secondaries because of the oxygen permeability of certain types of plastics. I've been using 5 gallon primo water jugs, which are labeled as #7 (other). I've not experienced any problems with crazy off flavors in my wine, but then again my tongue may be off.

Therefore I am proposing to collect the hard data!

1) Boiling 5 gallons of water to drive off any dissolved oxygen.

2) Taking a dissolved oxygen reading using the shiny new dissolved oxygen probe I just ordered for my Environmental Science Class.

3) Taking readings as often as I can, day to day, or at most a week apart, over the course of a year to determine if any oxygen is indeed penetrating in significant amounts.

4) Present the findings here to be published in the auspicious Journal of Homebrewology for all to see.

I <3 the scientific method. :)

geniz 12-13-2011 05:28 PM

Excellent. As a fellow plastic jug fermeterator, I'm looking forward to your findings

SteveHoward 12-13-2011 08:50 PM

I'm very interested in this. I'm a mythbusters kind of guy myself (which may be why I work an R&D job :) ). I'm always interested in testing what people have always heard or have always said :).

SenorPepe 12-13-2011 08:58 PM

Sweet! Any confounding factors at work? Does pH, viscosity, etc. affect how much dissolved oxygen will show up?

broadbill 12-13-2011 09:02 PM

May I offer some suggestions to make this a bit "tighter" scientifically?

Don't use water...the criticism will be that water in a plastic carboy does not have same characteristics in regard to oxygen permeability as does wine/beer in a carboy. This is probably a minor gripe...but doing the experiment with an actual material of interest makes it a better experiment.

Second...you are going to take measurements and get data...but how will you know if that data tells you something meaningful? You need a control that tells you that it is meaningful (and how meaningful is it?).
In this case you want to compare your data set using plastic to a sample where oxygen permeability is effectively nil (i.e. a glass carboy). Only by comparing the measurements from the plastic to the measurements from the glass will you know if there is a significant increase in dissolved oxygen in your liquid. You also correct for the intial amount of dissolved oxygen in the material at the start of the experiment.

Third, say you see a difference....what if that effect you saw only happens to that one plastic container you tested? You need to have at least two plastic containers to measure for good results (Three to five containers for even better statistical power!)

Since you are going to spend a year doing this, may as well do it right.

maffewl 12-13-2011 09:05 PM

I love the idea... only problem I see is that won't opening the carboy to take readings however often allow oxygen in each time thereby upping the readings? I agree as well that using water may not be the best test subject compared to an actual beer.

broadbill 12-14-2011 12:57 AM

Quote:

Originally Posted by maffewl (Post 3567986)
I love the idea... only problem I see is that won't opening the carboy to take readings however often allow oxygen in each time thereby upping the readings? I agree as well that using water may not be the best test subject compared to an actual beer.

Yet another reason why you need a control.... theoretically air would enter each by the same amount every time you took a reading...any differences you see could then be attributed to how the different containers let air through.

huesmann 12-14-2011 12:10 PM

Yeah, I think the OP needs to run a control sample in a glass carboy of the same size, taking measurements from both carboys with the same frequency.

brazedowl 12-14-2011 05:09 PM

Quote:

Originally Posted by maffewl (Post 3567986)
I love the idea... only problem I see is that won't opening the carboy to take readings however often allow oxygen in each time thereby upping the readings? I agree as well that using water may not be the best test subject compared to an actual beer.

Quote:

Originally Posted by broadbill (Post 3567973)
Don't use water...the criticism will be that water in a plastic carboy does not have same characteristics in regard to oxygen permeability as does wine/beer in a carboy. This is probably a minor gripe...but doing the experiment with an actual material of interest makes it a better experiment.

The problem with using beer/wine as a comparison is the fact that there won't bee free oxygen. The way that oxygen messes up beer/wine is that it combines with molecules in the brew and oxidizes it and therefore won't be floating around to be detected by my the probe.

Quote:

Originally Posted by huesmann (Post 3569865)
Yeah, I think the OP needs to run a control sample in a glass carboy of the same size, taking measurements from both carboys with the same frequency.

True yes. I'll try to locate one. This would also account for any Oxygen added while taking the sample. It should have the same amount enter for both as long as I take the sample for the same amount of time in the same manner for each sample.

Quote:

Originally Posted by broadbill (Post 3567973)
Third, say you see a difference....what if that effect you saw only happens to that one plastic container you tested? You need to have at least two plastic containers to measure for good results (Three to five containers for even better statistical power!)

Tis part of the plan. Did not write it in though. :)

Quote:

Originally Posted by SenorPepe (Post 3567952)
Sweet! Any confounding factors at work? Does pH, viscosity, etc. affect how much dissolved oxygen will show up?

They have an effect on the probe but it will be calibrated to work in tap water so the readings should be sound.

hbtasdfg 12-14-2011 07:38 PM

plastics do interact with the environment like that but very slowly so checking weekly is probably far too often. I'd wait 3 months before the first reading, start with lightly carbonated water, and test for loss of carbonation.

I would also seal the carboy with something other than an airlock, CO2 and oxygen can travel through the water in the airlock and the effect of this probably is much larger than travel through the plastic.

Find small plastic bottles, 2L size or so of different kinds of plastics and compare to a 1/2 gallon glass bottle, seal all of them hermetically for 3 months and later open and test carbonation level and for oxygen. It might take a couple years to notice much of a difference.


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