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I brewed batch # 34 and 35 on Saturday when the weather was nice over here. #34 was something close to a recipe I made about 10 times… heavy oatmeal stout. This time it had some lactose to make it a sweet stout. I made 6.5 gallons in my conical fermentor (Fast Ferment)… again have made that size or larger batches (it has a 7.5 gallon capacity) with out issue, but this time, the wife wakes me up at 630am on Sunday to tell me that there is beer all over the floor, and sure enough this was foam-overflowing for a solid 12 hours (I set up a blow off tube and mopped the floor), I really want to figure out why this happened… As I was kicking myself and mopping I was thinking of what could have caused this: I have four culprits I suspect, your advice is appreciated:

  1. As mentioned I had lactose in there (.75 lb for 6.5 gallon)… I never used lactose before. Also the recipe included adding 3 lbs LME as a “late addition”, so 15 min left in the boil… never saw that before, I thought it was a way to keep the sweetness…SG was 1.097
  2. I had a lot of trouble regulating the temp on the burner, in hindsight, I may have had the temp up too high since I was really close to boil-overs a few times
  3. As I was cooling the wort I entrained O2 in the pot in a different way, previously I would use a aeration stone (like in the fish tanks), this time I shook my cooling coils,and It really seemed to get more air in the mix, it was quite foamy…at the time I thought that wa a good idea.
  4. I used Safale S-04, typically I use Safale-05, but a wrong click on the Amazon got me the blue packets instead.

Thanks in advance, I really do not want this to happen again…


Did you control temperature during fermentation? Specifically, did you do something to keep it cool? Yeast is more active at higher temperatures, and fermentation produces heat, so it can become a runaway situation resulting in a very fast fermentation. The optimum temperature range for that yeast is 68 to 74 degrees F - that’s wort temperature. The wort will run several degrees hotter than the room. Keeping it toward the lower end of the optimum temperature range early in the fermentation, then allowing it to slowly rise toward the upper end of the range later has worked out well in my experience.

Ah yes… The dreadful air locker launch!
Very active yeast… Steve has you covered… My thought is a warm fermentation temp! Very happy yeast too!

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Yeah… no. I get the temperature thing, but this was in my kitchen (thus explaining my wife’s dismay)… indoors temperatures is always +/- 5 degrees here… not a large swing, even so this started at night when the thermostat was set for 64… Maybe the temp was high 60’s during the day… but I have made this before, fermented in the same kitchen in the summer and fall without the foam attack.

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Wort temperature can run quite a bit higher than room temperature, especially during a very active fermentation. I often ferment in a refrigerator. For a porter I currently have in the works, here is wort and refrigerator air temperature.


^^^ This. Big gravity beer fermenting just a touch too warm. You say you’ve never added the LME before? There’s some extra fuel for the blowout. The graph @Steve posted is very telling. Your 64 degree kitchen ain’t quite cool enough for such well-fed happy yeast! Been there before myself with a high gravity beer. I always doing the initial fermentation with containment.

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Yeah, I get it, but I have made a 6.5 gallon batch of this stuff, and the SG was 1.110… and it was summer… and this did not happen…

If I just let it go and say “Things like this happen”, my wife will tell me to ferment in the garage.

This is bound to happen from time to time. You have a healthy, vigorous fermentation taking place.

Aside from some temperature control as others have suggested:

  1. Use a blow-off tube until the fermentation slows down

  2. Try using Fermcap-S.

The other variable is the 04 vs 05.

I think that is the answer. The difference between the yeasts. Almost has to be.

Blow over hose. Time to build your own brew area. Aka men cave. My wife dont like them smell of yeast fermenting. Now got my own room. She is happy


1gal headspace is not a lot, especially with a nice healthy yeast. Couple that with warm fermentation temps and blow offs occur. Especially on high OG beers.
It’s cyclical. The yeast create heat which results in more active yeast which creates more heat which means the yeast get more active…

What was the temp of the wort at pitching?

I got the Wort down to about 70 degrees.

Did you measure the temp? Pitching too warm will result in increased activity.
If you don’t have anything accurate to measure temps with I would suggest This thermapen . It’s instant read and very accurate. They often go on sale too.

Yep I have a FastFerment fermentor, and it has a thermowell. I did not write down the temp, but I recall it was less than 70, since the upper range of the yeast was 74… that was my main concern (at the time)

Whatever the root cause of your volcano is, a best practice would be to use a blow-off tube and a containment vessel as others have said. At least for the first few days. Cheap insurance that will protect you from your wife’s ire!

Also, I use this Inkbird thermometer. $12 vs $80. The only real difference I see is 4-7 second read time for Inkbird and 2-3 seconds for Thermopen.

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