Explosive fermentation

[Teufelhunde]

Yesterday I brewed 5 gals of a Mosaic IPA. It started bubbling in the airlock after about 18 hours, pretty normal. About 4 hours later, the airlock is going crazy for a short while (almost constant bubbles), then being stagnant for a while. I got a strong flashlight (to be able to see through the white bucket, and got the light just right, and I could see the krausen rising about 5 inches off the top surface of the beer.

A bit later, I checked on it again, and there is an airlock full of foam and foam all over the top of the bucket and running down the sides. I rigged up a blow off tube running into a jar of sanitizer and cleaned up the mess. As I have been checking on it to make sure I don't have more of a mess to clean, I noticed that it is bubbling regularly for a while, then will go crazy bubbling like mad, then slow a bit, etc.

I've got a couple of questions.....

1) I know that some fermentations go crazy like this, what causes it? I'm not doing anything unusual, and I have brewed this recipe before without issue, albeit with LME instead of the DME I used this time.

2) As a general rule, will this behavior continue until fermentation is done, or is it reasonable to expect it to settle down so I can put the airlock back in? I used my bottling tubing for the blowoff and have another 5 gals I was going to bottle on Saturday.

TIA for any input.....

Lon

 

[brewdude88]

If the fermentations going that strong, it should stop blowing foam in 24-48 hours.

As to what caused it, any number of things. The one time I've had an explosive fermentation (launched a bucket lid, 1 cat, 2 dogs and a human to the ceiling) was a porter I've made a lot. The one difference I could find was a warmer yeast pitch than I usually do. The temp kind of ran away on that one. That was the day I got a chest freezer for temp control, never happened since.

 

[bkboiler]

Wort fermentability, yeast strain, yeast viability (energy reserves among other factors), yeast metabolism (did they recently wake up or are they already running?), Yeast nutrients, O2 availability, temperature, pressure, and finally OG and wort pH...
But that is not an exhaustive list...
WLP99 San Diego super yeast was my craziest ferment...12 hours and it clogged the airlock and shot it up into the cabinet it was under ...luckily the krausen didnt go everywhere...

 

[Teufelhunde]

If the fermentations going that strong, it should stop blowing foam in 24-48 hours.

As to what caused it, any number of things. The one time I've had an explosive fermentation (launched a bucket lid, 1 cat, 2 dogs and a human to the ceiling) was a porter I've made a lot. The one difference I could find was a warmer yeast pitch than I usually do. The temp kind of ran away on that one. That was the day I got a chest freezer for temp control, never happened since.

In my case, I don't think it's a temperature issue. I put my bucket into a mini-fridge with inkbird set at 65, and the tape thermometer on the side of the bucket is indicating that the temp in the bucket is 68-70..... I just looked at it, and it is bubbling through the blow off like someone has the tube in their mouth blowing bubbles in the sanitizer.....

 

[Teufelhunde]

Wort fermentability, yeast strain, yeast viability (energy reserves among other factors), yeast metabolism (did they recently wake up or are they already running?), Yeast nutrients, O2 availability, temperature, pressure, and finally OG and wort pH...
But that is not an exhaustive list...
WLP99 San Diego super yeast was my craziest ferment...12 hours and it clogged the airlock and shot it up into the cabinet it was under ...luckily the krausen didnt go everywhere...

Wow, for a hobby, there is surely a LOT to learn about this, huh? I am using Fermentis Safale US-04 that this recipe calls for. The only thing I can think of is that this is a high OG recipe....it expects 1.070....I read 1.058 but then I really don't trust my hydrometer, it seems to always read a bit light compared to what's expected.

 

[VikeMan]

1) I know that some fermentations go crazy like this, what causes it? I'm not doing anything unusual, and I have brewed this recipe before without issue, albeit with LME instead of the DME I used this time.

There are lots of variables, as already mentioned. But when I see "LME instead of the DME I used this time," it makes me wonder... did you take a recipe and substitute the same weight of DME for the LME?

 

[Teufelhunde]

There are lots of variables, as already mentioned. But when I see "LME instead of the DME I used this time," it makes me wonder... did you take a recipe and substitute the same weight of DME for the LME?

Nope, the weight was modified for the difference in sugar content between the two...

 

[VikeMan]

Hmm. FWIW, here are my rules of thumb for avoiding blowoff trouble...

1) Adequate headspace in the fermenter. Total fermenter volume >= 1.3 x wort volume.
2) Fermentation temperature control.
3) For high gravity worts (say 1.060-ish or higher assuming #1 and #2 above are covered), use a blowoff hose/reservoir instead of a regular airlock.

 

[VikeMan]

The only thing I can think of is that this is a high OG recipe....it expects 1.070....I read 1.058 but then I really don't trust my hydrometer, it seems to always read a bit light compared to what's expected.

With an extract recipe, it's pretty hard to not hit close to the target OG. When you get a reading significantly lower than planned, here are several possibilities, alone or in combination...

- You didn't get all the extract into the kettle (LME stuck in the jug?)
- You topped off with water to more than the target volume
- You didn't mix the top-off water with the wort thoroughly before measuring the OG
- You measured the OG while the wort (and top off water) was still hot, and didn't adjust the reading for temperature.
- Some wort was left behind in the bottom of the kettle, so more water was used to top off to reach the target volume.
- Your hydrometer is inaccurate (try checking it with plain water)
- Operator error on the gravity reading
- Recipe/Software problem

 

[Teufelhunde]

Hmm. FWIW, here are my rules of thumb for avoiding blowoff trouble...

1) Adequate headspace in the fermenter. Total fermenter volume >= 1.3 x wort volume.
2) Fermentation temperature control.
3) For high gravity worts (say 1.060-ish or higher assuming #1 and #2 above are covered), use a blowoff hose/reservoir instead of a regular airlock.

1) My fermenter is 6.5 gallons for 5 gal batches, so I think that is covered
2) The bucket is in a mini fridge held at 65, so that's good
3) I think this is likely the issue.......The recipe calls for 1.070....my hydrometer measured 1.058.....per your next post I just checked the hydrometer with 70 degree RO water and it read .987........a .013 difference......addint the .013 to 1.058, I get 1.071

Next time I do this recipe (and I will, it is great), I'll just set up the blow off hose from the git-go

Thanks for the input, I really do appreciate it......

Lon

 

[Teufelhunde]

I though I should come back and update this thread.....

About 30 hours after the very vigorous fermentation start, just like someone flipped a switch, it was done, It just stopped......today, I took it out of the mini-fridge and put it on the shelf at room temp and checked the gravity. After adjusting for my less than accurate hydrometer it is at 1.017, right where I would expect it to be...I tasted it, and it tastes great, so if the second FG test shows that it is stable, it is on to the dry hopping.....

 

[VikeMan]

I tasted it, and it tastes great, so if the second FG test shows that it is stable, it is on to the dry hopping.....

You actually don't have to wait for FG to be stable before dry hopping.

 

[Teufelhunde]

You actually don't have to wait for FG to be stable before dry hopping.

Yep, I have dry hopped with a little bit of fermentation still happening before, but as a general rule, I wait......