Fermentation Time?

[rod734]

I brewed an IPA one day, the next day I brewed a Porter, and the next day I brewed an APA. I know activity in the air lock dosn't mean the yeast is done, but the APA had airlock activity for three days, the IPA for seven days and the Porter is still going after 15 days. I racked the IPA to a keg and dry hopped it, because I was out of beer and needed to rush it. I'm leaving the APA in primary for three weeks then I will keg it and let it cond. for a few weeks.
Is it normal for a Porter to take longer? I used the same yeast (nottingham) in all three and fermented @ 60 degrees F. I'm not really worried about it, just curious. And with what I have experienced in the past year brewing, how do the big breweries crank out beer on a time schedual? I know it's all about control and about the only variable in my procedure may have been a couple degrees in my pitching temp.

 

[KAMMEE]

Check the gravity, its the only way to know its actually finished. If you see airlock activity its probably just CO2 coming out of solution. There is usually between 1-1.5 volumes of dissolved CO2 in your beer after fermentation is complete and letting it sit for a while will allow some of that to come out of solution and cause bubbles in the airlock. Nottingham is a fast finisher, usually should be done within 7 days, even when used at 60F.

 

[rod734]

the air lock finally stopped bubbling, I brewed this on 4/11 and had stedy activity all this time