by Christopher Weeks on Fri May 11, 2018 7:30 am
I agree that it's fine for at least most vegetable fermentation processes. Your bacteria are going to kick out CO2 that will buoy toward the surface. Some of those bubbles will encounter the large bubble under the weight and cause some of that gas to displace out around the edges and up to the head of the vessel. At first, the air under the weight is our normal air mixture, but over a short time, the gas will skew toward higher and higher concentrations of CO2. Once it's essentially all CO2, there's no worry.
However, if you're removing the weight and interacting with the ferment, then each time you do that, the bubble starts over as fresh air and once you're well into the fermentation cycle, a lot less CO2 is being produced. It's exactly the same situation as fermenting under an air-lock of any kind.