Fast primary?

[ZehBaron]

So I've brewed 6 batches of beer as of now, and for the most part I've been steadily improving and having relatively few problems and mistakes. However, one thing has continued to bugger me: I keep getting remarkably quick primary fermentations. Every batch I've brewed so far has begun showing signs of vigorous fermentation within 12 hours of pitching. Following that, the airlock will bubble happily for no more than 24 hours-- but then over the course of a few hours bubbling will slow down rapidly and soon comes to a screeching halt.

Now, I know that the absence of bubbles doesn't by any stretch mean that fermentation is over, but could airlock activity stopping that quickly be right? At first I thought it was the yeast strain (Muntion & Fison dry ale yeast), but then I used a Wyeast hefe-weisse yeast on a different batch and got the same results. Ambient temperature during primary has always been between 65F and 68F, and the liquid crystal thermometer on the side of the fermentor bucket never reads more than 71F, even during Kraeusen.

I can't say this short primary has ever caused noteable problems; OG and FG readings match the calculated estimates, and the brews certainly taste good. But just because this abnormality bugs me, I've tinkered with all sorts of variables to see if I can affect it: different yeast starter sizes, aeration rates, amounts of malt, etc.-- but nothing seems to have any effect.

So, are my short primaries a problem? And even if not, any clues as to what's causing them? Thanks a bunch.

 

[hercher]

Are you fermenting in a plastic bucket? If so, perhaps the seal on the lid is not perfect, so when fermentation slows down, the CO2 is escaping through there rather than the airlock. Remember, the gas is going to follow the path of least resistance.

You don't mention how much yeast you are pitching, but that could produce these results.

If the beer tastes fine, you have nothing to worry about except the jealously of other homebrewers.