Changes

Different airlocks and vessel materials diffuse oxygen at different rates. For example, a set of experiments published by Dr. Enrich L. Gibbs at BetterBottle™ showed that rubber stoppers prevented oxygen transfer more effectively than silicone stoppers, plastic stoppers, and both the "3 piece" airlock and "S" airlock. Solid bungs, however, can build up pressure inside the fermenter as the beer slowly ferments, and can pop off due to the pressure (and can cause messes if the vessel becomes pressurized too much). Weekly degassing for a few months while the beer ages is one option with solid bungs. See the [http://www.better-bottle.com/pdf/ClosuresOxygenPassageStudy.pdf BetterBottle™ paper for more information]. Raj Apte found that HDPE buckets let in farm more oxygen than carboy setups, and taking into account the high surface area to volume ratio in homebrew setups versus full size barrels, oxygen exposure over time on the homebrew level can be a difficult issue to solve. For example, Apte attempted using wooden dowels as stoppers in carboys, and found that it let in about the same amount of oxygen as wooden tanks at Rodenbach. However, the swelling of the wooden dowels led some people to crack or destroy glass carboys (therefore this method is not recommended) <ref name="Apte">[http://web.archive.org/web/20100410025103/http://www2.parc.com/emdl/members/apte/flemishredale.shtml "How to Make Sour Ale: an inquiry". Raj B Apte. 2004. Retrieved 1/1/2016.]</ref>.