Bilsch
Well-Known Member
- Joined
- May 4, 2015
- Messages
- 1,677
- Reaction score
- 1,517
Good data but not accurate or even relevant when there is a pressure differential. Ferment under (even relatively low) pressure and you won't care about these data one whit. Of course, none of these numbers are large enough to make any difference to oxidation extent anyway.
Actually pressure differential (CO2 pressure or any other gas except O2) inside the container has no effect on the oxygen diffusion through the polymer. The concentration gradient or difference in the partial pressure of oxygen on the outside vs the inside of the container is the only relevant force. You could have literally a million pounds of CO2 pressure inside and it would have zero effect on the oxygen flow through the plastic. Furthermore the oxygen will continue to flow in, only limited by the oxygen permeability of the cap, until the concentration of oxygen inside is the same as on the outside. The only way to stop it is if the container is fully impermeable to oxygen such as stainless, aluminum, glass, steel etc. Even a keg is not perfect since it has o-ring seals that are more or less permeable depending on the material. Silicone is the worst, Buna-N is one of the better materials but still pervious to a small extent. Even the seal on bottle caps will pass a small amount of gasses laterally through the seal.