oxygen permeability of plastic - Page 4

MachineShopBrewing · 02-06-2012, 11:27 PM

I was able to get gas permeability information from the Ale Pail manufacturer.

This is the chart that they gave me:

GAS RATE(cc/mil/24hrs/100in^2)

CO2 345
Ethane 236
Hydrogen 321
Natural Gas 113
Oxygen 111
Freon 12 95
Helium 247
Nitrogen 53
Sulfur Dioxide 306

I have no idea how to relate cc/mil/24hrs/100in^2 into ppb or ppm, so I am hoping you chemistry guys can help me out there.

Oldsock · 03-15-2012, 01:30 PM

The numbers arrive and the thread dies?

To make those numbers usable you would have to determine the surface area of an ale pail. http://www.homebrewtalk.com/f11/ale-pail-dimensions-72525/ Let’s assume it is actually just a cylinder with a diameter of 11 inches and a height of 17.5. Which is 795 In^2. That means that we need to multiply the numbers supplied by 7.95, so 882 ml of oxygen every 24 hours… that doesn’t sound good. From there you would need to figure out how much oxygen that is compared to how much beer is in the fermentor.

As someone else said, the smaller the fermentor is the more oxygen it will let in because of the higher surface to volume ratio.

My bigger concern with buckets has always been the seal. If anyone hasn’t seen it Better Bottle did an oxygen permeability study on airlocks and bungs: http://www.better-bottle.com/pdf/Closures_Oxygen_Passage_Study.pdf

dwoodfield3 · 03-30-2012, 07:54 PM

Supposing you would like to bulk condition your beer in a plastic food grade bucket with lid from the local HB store, could you not glue a layer of Mylar Space Blanket around bucket, lid, and bottom of bucket... that way even though the plastic container is not strictly oxygen impermeable, the oxygen will never touch the outsides of the container because of the space blanket. If space blankets can work as a barrier against hydrogen and helium, then by all rights it should stop oxygen too no? Or is the oxygen permeability of these buckets negligible anyway for long term beer conditioning? Just a thought....

Dom

SmallBatchBrew · 03-30-2012, 10:53 PM

Quote:

Originally Posted by Homercidal

However if we use a secondary, either bucket or carboy, we leave the CO2 protection and introduce air to the beer while racking. If we don't purge the secondary with CO2, then the beer is also in long-term contact with O2. The amount depends on the amount of headspace. In a 5 gallon carboy, it might not be much. In a bucket, it's going to be a very substantial surface area and a large enough volume of air.

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

kingwood-kid · 03-31-2012, 12:27 AM

Quote:

Originally Posted by SmallBatchBrew

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

I often add a tiny amount of table sugar (less than I use to carbonate) when racking to make this thin layer a little thicker. I can't tell you it works, but I'm pretty sure it does no harm.