What about limiting O2 during primary fermentation? I know you want to start with lots for the yeasties to divide, but don't you need an airtight seal (and airlock) once it gets going? I ask, because my carboys always foam out while in primary, and I'd like to try buckets, just not sure how they work.
Carboys can do that. If there is a reason that reduces the free flow of the CO2, maybe capping or whatever, as the residual pressure builds, eventually it will erupt and the tiny amount of nucleation when the pressure causes the eruption will cause it to flow until the equilibrium returns......
With the bigger air liquid interface in a bucket, anything that causes a cap has more space to break under similar circumstances and hopefully enough space for the erupting co2 so that any bubbles pop and the co2 just discharges out the airlock.....
The theory is just a basic high school physics lesson where the open surface area isnt funnelled into a small area creating a jet to push out through the airlock or force it and the bung out.......
It can be ameliorated by frequent movement which is where early stage aeration or just swirling or even just vibrating thw whole fermenter comes in.
It helps nucleation enough to reduced the build up of dissolved CO2 so that you get a greater steady flow of it during the early fermentation when its production is at its greatest, ergo the chance of eruption is greatly reduced.
There is at least with traditionals, anecdotal evidence, that stir plates can even reduce down fermentation times. Some have posted about using them with show meads where there has been no nutrients added but the quick exhaustion and death of yeast cells combined with the constant motion have fermented such brews in a couple of weeks, rather than the many months posted about with static batches of same/similar brews i.e. the quick exhaustion and death of the yeast cells provides enough base nutrient for the newly budded cells to do their thing etc.......
Practically ? You won't be able to stir plate or use a lab swirler for batches much bigger than a gallon for size and equipment reasons (unless you're one hell of a good production engineer), so we generally resort to aerating/stirring/swirling as many times a day as we can - 2 or 3 times for most people.......
Hopefully that makes sense (it does to me at least) and hopefully you follow my poor explanation of this effect.......