Ferment in Plastic or Glass?

Pellets
Dry and liquid yeast
Primary
extended whirlpool
racking
digital temp controller
vented xfer

...this is fun!

 

How could you forget the all time leader? Rehydrating dry yeast v not rehydrating.

 

Shame on me...maybe I could redeem myself by mentioning First Wort Hopping (FWH)

 

I would think in advance about how to carry them when they are full. Many people use milk crates, some buy the brew haulers. Don't rely on the carboy handles.

Also: pellets, primary, whirlpool, spigot, vented, rehydrated, and not FWH

 

Agreed you for sure want to plan ahead. With 5 gallons of in there it is very heavy. I use the brew hauler myself. Handles look pretty handy but I feel much more secure knowing there is straps underneath the carboy.

 

From a functional sense, it is absolutely correct because the differences in material permeability are orders of magnitude less than the permeability at the seal.

Here is where you have proven my point. Most bungs that homebrewers use are made of silicone and the seal around the lid is some type of rubber. Both are MUCH more permeable than the material of which the fermenter is made. Plus you have to take into consideration multiple material interfaces. With a carboy you have two. Where the silicone bung interfaces with the carboy and where the bung interfaces with the airlock. With a plastic bucket you have those two interfaces PLUS the lid seal interface. The last of which is MUCH longer than either of the first two.

 

The surface area of the entire HDPE bucket is orders of magnitude larger than the seal of the lid.

 

The issue at hand is comparing the amount of ingress through the vessel wall versus the total amount of ingress for the vessel as a whole, complete with closures. Feel free to extrapolate the data that you provided for the total surface area of any vessel and compare that to total vessel permeability and you will see my point.

 

I don't know about you all, but I actually like helping new homebrewers or just those with questions. It never gets old for me. I feel like even though there are a lot more resources for them than I had when I started the hobby, those resources often bring up additional questions that are difficult to answer on one's own. At the very least, I feel like I can provide them direction without holding their hand by giving them a link or two to read.

 

A standard HDPE bucket fermenter has surface area of ~ 0.066 m^2 and a thickness of ~ 6 mm. Take the average permeability (~ 67) and multiply by the surface area and divide by the thickness (67 x 0.066 / 6 = vol. O2 per day in cm^3) and you get 0.737 cm^3 of O2 passing through the bucket wall per day. Per week that is about 5.2 cm^3 (~ 0.0052 L) of O2. By molarity, this is 0.000047 mol O2, or 0.0015 g of O2 per week.

Cheers!

 

And the total permeability of that same vessel is?

 

Show me your math for the amount of oxygen ingress through a bucket lid seal and I will respond to you query.

 

The permeability of the vessel, as a whole, is 220 mg of O2 per liter per year. It is 78 mg total for the entire 6 gallon vessel (22.7 liters), so 3.4 mg of O2 per liter per year is coming through the walls. The rest is, therefor, coming through the seals.

 

Or...just use an open fermenter
https://www.beeradvocate.com/community/threads/why-is-bigfoot-fermented-in-open-containers.174670/

 

I open ferment all my active primaries. Never done a side-by-side, but I figure that less pressure equals happier yeast.

 

Brulosophy podcast recently reported on a test that showed detectable differences between beer from glass and plastic, and there was a tendency to prefer the glass. I continue to use plastic because (1) I like my beer and (2) I like my fingers and toes.

 

There are four parts to this exBEERiment, if you are interersted (the first is PET carboy versus plastic bucket):

http://brulosophy.com/2014/10/14/the-impact-of-fermentation-vessel-exbeeriment-results/
http://brulosophy.com/2016/05/16/fe...stic-pet-vs-glass-carboy-exbeeriment-results/
http://brulosophy.com/2016/07/11/fe...ss-steel-vs-glass-carboy-exbeeriment-results/
http://brulosophy.com/2017/02/13/fe...orny-keg-vs-glass-carboy-exbeeriment-results/

 

I'm not sure that is entirely accurate when stated that way. Unless there are additional details in Jeff's book, the slide itself has very little info about how those measurements were taken.

Were the vessels in question sealed and left for a period of one year, then measured? Were they use in a more real world scenario (opened to take samples, ect...)? Did all vessels start with a split batch of from the same wort (O2 levels could have started different)?

Unless I missed it, the major increase in O2 is not identified as a seal issue in the deck. So the major increase could have been when a bucket is opened for samples, the whole top of the wort would be exposed to O2 vs the small opening of a carboy or bung hole.

 

I wholly agree. Is it known that this value was obtained via measurement? If so, what was the test instrument? And as you pointed out in your post the conditions of measurement need to be detailed.

There are technical details on the Better Bottle website and measuring O2 diffusion over time requires sophisticated equipment.

Cheers!