Well for one thing, bubbles mean absolutely nothing
. All it means is that co2 is coming out of the airlock, it doesn't correspond to points of gravity lost or anything else. .Gas expands and contracts due to all manner of things, temp swings, changes in atmospheric pressure, or gas gets released from the trub layer due to traffic rumbling on the road, the vacuum cleaner going, the dog trying to hump the fermenter....That's WHY we tell you that airlock activity isn't a good indicator of whether or not you have fermentation . Because SO MANY other things can cause airlocks to start AND stop....That's why I basically say, ignore your airlock....
Take a gravity reading instead...more than likely you'll find they're pretty similar in terms of gravity.
And if they're not, that doesn't mean anything else either.
We're dealing with living micro-organisms, and tons of affecting variables in each fermenter. Slight changes in temp from where sunlight might hit one fermenter differently over another by even a degree; proteins in solution, phases of the moon, yadda yadda yadda.....there's a lot going on.
There is nothing "typical" in brewing...No two fermentations are ever exactly the same. Even with the same recipe/yeast, etc. Too many variables at play in any given day.
When we are dealing with living creatures, there is a wild card factor in play..Just like with other animals, including humans...No two behave the same.
You can split a batch in half put them in 2 identical carboys, and pitch equal amounts of yeast from the same starter...and have them act completely differently...for some reason on a subatomic level...think about it...yeasties are small...1 degree difference in temp to us, could be a 50 degree difference to them...one fermenter can be a couple degrees warmer because it's closer to a vent all the way across the room and the yeasties take off...
Someone, Grinder I think posted a pic once of 2 carboys touching each other, and one one of the carboys the krausen had formed only on the side that touched the other carboy...probably reacting to the heat of the first fermentation....but it was like symbiotic or something...
Yeasts are like teenagers, swmbos, and humans in general, they have their own individual way of doing things. So it's never a good idea to compare one fermentation to another.
That's why I tell people not to read meaning into any so-called "signs of activity" other than gravity changes. Because they are for various reasons never usually a direct association with what the yeast is actually doing in the beer. They can just as easily be affected by environmental conditions as anything else.
All that matters is that the yeast is eating the sugars, (which 99.99999% of the time they are) not how the airlock bubble or doesn't bubble or even what the krausen does or doesn't do, or looks like for that matter.
Activity, action, bubbles, even krausen can be affected by the envoironment just as much as it being caused by the yeast...so going by that is NOT reliable.
If you want to know what's going on with your beer, then take a gravity reading. The only way to truly know what is going on in your fermenter is with your hydrometer.
Like I said here in my blog, which I encourage you to read, Think evaluation before action
you sure as HELL wouldn't want a doctor to start cutting on you unless he used the proper diagnostic instuments like x-rays first, right? You wouldn't want him to just take a look in your eyes briefly and say "I'm cutting into your chest first thing in the morning." You would want them to use the right diagnostic tools
before the slice and dice, right? You'd cry malpractice, I would hope, if they didn't say they were sending you for an MRI and other things before going in....
Going by airlocks is the same thing. There's still things going on under the surface despite what an airlock is or isn't doing.