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  1. Why did this happen?

  2. Is this bad? Aside from wasting beer, it seems to me that this would invite infection? If it means anything, I smelled the airlock and it seemed mostly vinegar, but tasting the airlock (and spitting it out) revealed no vinegar taste, more of a terrible beer taste.

Background: This is my fourth batch of extract brewing. This is the second time I used an aeration stone. I pitched the yeast on Sunday around 4pm. I believe it was fine this morning (Tuesday) at 8am, although I might not have actually looked. At 10am it was overflowing. I followed the kit instructions perfectly and had 5 gallons of wart in the 6 gallon bucket.

I sanitized a new airlock and replaced it.

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up vote 5 down vote accepted

Looks like a vigorous fermentation to me. Consider switching to a blowoff tube for the primary. Its nothing bad, and I wouldn't worry about infection at this point, it will settle down in a few days to a week.

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To add on to that, if you can't/don't switch to a blowoff, make sure it doesn't get clogged. Periodically check every several hours to make sure you see the airlock moving (until fermentation completes of course). If the lid starts to expand upward, and the airlock isn't moving, you may have a geyser waiting to happen. You'd need to safely vent it at that point and clean out the airlock. – Scott Jun 4 '13 at 19:33

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