Counting the bubbles?
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Scut_Monkey
Well-Known Member
Most likely they are talking about counting the bubbling on the airlock. Also known as airlock activity. It's a crude way to determine if fermentation is going on by the release of CO2.
Brew_Master
Active Member
Why do you say "unreliable"?. I always find it a great reassurance to see bubbling a few hours after pitching my yeast.
BrewKnurd
Well-Known Member
Aaaaaaaand here comes revvy!
BrewKnurd
Well-Known Member
Brew_Master said:
Its unreliable because bubbling can happen without it being fermentation, and fermentation can happen without you seeing bubbles. Sounds unreliable to me.
Scut_Monkey
Well-Known Member
Ditto. The wort can release dissolved CO2 causing airlock activity that is misleading. On the other hand, unless the fermenter is air tight the airlock may not move at all when fermentation is actually happening. The best way to monitor fermentation is with SG readings. However, airlock activity is a CRUDE way to monitor fermentation.
Brew_Master
Active Member
Well that's the point of an AIRLOCK to make the fermenter airtight, and yeah I know it can't be as reliable as an SG reading but you have to wait a day or two between readings to tell if activity has ceased but usually if there are no bubbles that's an instant hint that fermentation has stopped or is really really slow
Heineken_Draught
Active Member
And usually after degassing there should be no more CO2 to bubble.
BrewKnurd
Well-Known Member
Well that's the point of an AIRLOCK to make the fermenter airtight, and yeah I know it can't be as reliable as an SG reading but you have to wait a day or two between readings to tell if activity has ceased but usually if there are no bubbles that's an instant hint that fermentation has stopped or is really really slow
Exactly. Its a hint. Not a guarantee of anything, and that's the point people are trying to make when they say the airlock is an unreliable sign of fermentation.
In order to see airlock activity for a given fermentation, all of the following must be true:
1) fermentation occurs, producing CO2
2) fermenter is sufficiently sealed so that CO2 has no significant escape path other than through the airlock/blowoff tube
3) you happen to check the airlock for activity frequently enough/long enough/at the right time to witness the release of CO2
So if you didn't quite seal your fermenter, or you just happen to check at the wrong times, you can certainly go through a completely successful fermentation without ever seeing a bubble.
In addition, there are a number of things that could cause airlock activity outside of active fermentation, the most common of which are probably:
1) your fermenter warmed up a little, and the gas in the vapor space expanded, building pressure and causing gas to vent
2) your fermenter warmed up a little, resulting in gas coming out of solution, since gas is less soluble at high temperatures.
So yes, airlock is a hint. If you had two fermenters sitting next to each other and one had a bubbling airlock and one didn't, and you had to guess which one was actively fermenting, you would guess the one with the bubbling airlock, for sure. But airlock activity is not a sure fire sign one way or the other, and the reason this gets stressed on this board is because of the large number of "OMG, my beer isn't fermenting" threads that end up with "oh, it turns out everything was fine. :-D
DrJerryrigger
Well-Known Member
So assuming barometric pressure and temperature are stable, I would think that the water would become fully saturated with CO2. Once this happens counting the bubbles could be a highly accurate measurement of fermentation.
If you know the barometric pressure and temp you could calculate the mass of each bubble, and the amount of sugar needed to produce that amount. It would seem this in the only way to calculate a continuous rate of fermentation. The barometric pressure changing all the time would make this unreliable, or at least very difficult to calculate. Changing temperatures would also alter the dissolved CO2, another thing that would need to be factored out. But unless you've got a bunch of algae growing in there, it would seem that this could be a very useful tool.
Please correct me if I'm missing something here.
I do see why it would be bad to tell a new brewer to just count bubbles. If the barometric pressure jumped up, and the temp of the wine dropped; you'd think it had stopped.
If you know the barometric pressure and temp you could calculate the mass of each bubble, and the amount of sugar needed to produce that amount. It would seem this in the only way to calculate a continuous rate of fermentation. The barometric pressure changing all the time would make this unreliable, or at least very difficult to calculate. Changing temperatures would also alter the dissolved CO2, another thing that would need to be factored out. But unless you've got a bunch of algae growing in there, it would seem that this could be a very useful tool.
Please correct me if I'm missing something here.
I do see why it would be bad to tell a new brewer to just count bubbles. If the barometric pressure jumped up, and the temp of the wine dropped; you'd think it had stopped.
Here's what I've found, so far.
I started brewing using a glass carboy. Seals tight, the glass doesn't flex (visibly). So long as temperature remains constant, I can assume bubbles = activity- not necessarily CURRENT activity, just evidence that there was CO2 production, and gas was displaced. Shaking a fermentation vessel weeks after fermentation ceases will cause airlock activity due to release of dissolved CO2. Evidence of fermentation, just very late in coming.
Plastic vessels are even less reliable... they flex. You pick one up (better bottle) by the neck, and the bottle elongates, causing suckback. Put it down, and you have airlock activity. Bump it, you have airlock activity.
And, in case you're wondering- hold a warm body part up to the glass/plastic, on the gas side (top side). The warmth of your body is enough to cause the gas in the vessel to expand and make activity in the lock. Same thing can happen just being in the same room as it long enough. You change the temp, you change the volume that the gas occupies. It goes somewhere.
In a professional environment, however, you could definitely use a flow-meter hooked up to a pressure release valve to monitor the progress of a fermentation. You'd have to make sure the contents were being agitated (less dissolved CO2), and under precise temperature control, for starters. The tanks would have to be perfectly sealed, also. In fact... I believe I read about commercial wineries doing this. But I do dream a lot about making wine while sleeping, so maybe I'm making that up >.>
I started brewing using a glass carboy. Seals tight, the glass doesn't flex (visibly). So long as temperature remains constant, I can assume bubbles = activity- not necessarily CURRENT activity, just evidence that there was CO2 production, and gas was displaced. Shaking a fermentation vessel weeks after fermentation ceases will cause airlock activity due to release of dissolved CO2. Evidence of fermentation, just very late in coming.
Plastic vessels are even less reliable... they flex. You pick one up (better bottle) by the neck, and the bottle elongates, causing suckback. Put it down, and you have airlock activity. Bump it, you have airlock activity.
And, in case you're wondering- hold a warm body part up to the glass/plastic, on the gas side (top side). The warmth of your body is enough to cause the gas in the vessel to expand and make activity in the lock. Same thing can happen just being in the same room as it long enough. You change the temp, you change the volume that the gas occupies. It goes somewhere.
In a professional environment, however, you could definitely use a flow-meter hooked up to a pressure release valve to monitor the progress of a fermentation. You'd have to make sure the contents were being agitated (less dissolved CO2), and under precise temperature control, for starters. The tanks would have to be perfectly sealed, also. In fact... I believe I read about commercial wineries doing this. But I do dream a lot about making wine while sleeping, so maybe I'm making that up >.>
