CO2 Production and Fermentation

[MattyWeiss]

Sorry if this is something that was answered elsewhere, I tried looking around.

I'm about 10 days into my first batch of homebrew fermenting and still see that there is CO2 being made from the fermentation process. It hasn't been actively bubbling for a while, but you can see the pressure in the airlock pushing the water to one side.

Now, I'm not worried or anything, this is more just a question about the science of the process.

About a day ago I opened the bucket to take a look and take a hydrometer reading. Everything looked great, krausen had fallen and just some yeast solids floating around. Checked the gravity and got 1.012 (my OG was 1.042). I expect (hope) it drops down a little more still, but know this is closer to my FG. Obviously with opening the bucket that layer of CO2 and the pressure in the bucket dropped. When I put the lid back on, with the lack of pressure, the water was evenly distributed in the airlock.

Last time I looked, the bucket is pressurized again and the water is pushed to one side of he airlock. I know by opening the bucket some oxygen may have affected the fermentation, but upon hitting your final gravity, will CO2 production stop?

Again, I'm not worried, and know to give it more time anyway, I'm just more curious about the science behind the process. When fermentation is complete (as in your FG is where it is supposed to be) does the yeast produce any CO2 at all, or is there always going to be a small amount?

 

[jwalk4]

There might be some fermentation/conditioning still taking place that would produce some gas, but you would be surprised at the effect air temperature has on the internal pressure of your bucket.

It doesn't take much to hold the plastic thimble on your three piece up.

That's why most will say that air lock activity is not evidence of fermentation.

FWIW, 1.012 is a pretty good fg. What type of beer?

 

[RM-MN]

The part of fermentation that produces CO2 is usually done by the third or fourth day but your resulting beer can hold a tremendous amount of CO2 dissolved in it for a while. It will eventually outgas which can make your airlock bubble some and that can go on for days but the yeast isn't producing any more CO2 at that point.

 

[MattyWeiss]

There might be some fermentation/conditioning still taking place that would produce some gas, but you would be surprised at the effect air temperature has on the internal pressure of your bucket.

It doesn't take much to hold the plastic thimble on your three piece up.

That's why most will say that air lock activity is not evidence of fermentation.

FWIW, 1.012 is a pretty good fg. What type of beer?

Amber Ale. I figured it was probably done, but wouldn't mind if it dropped just a tiny bit more. I think with my OG at 1.042 I'm sitting at just under 4% abv if I'm calculating correct. Was hoping to push it above 4.

According to my recipe, my OG was exactly what it was supposed to be though so overall I'm happy. Took a taste of that sample and it was pretty good too.