3787 Blowoff

Ingredients
1

I pitched the dregs of a 2.5 liter starter on Friday around midnight into 5.15 gallons of Belgian Blonde in a 10 gallon corny keg.  7.5 hours later, it was fermenting vigorously and had already dropped about 5 points.  When I checked on it this morning (about 30 hours in), it was blowing off and had dropped 30 points.

I use 3787 a lot and know it produces a large krausen, but I’ve never seen blowoff before when fermenting a 5 gallon batch in a 10 gallon fermentor.  That’s crazy.

And I’m fermenting it a bit cooler than usual at 67°.

2

I have had similar unexplainable fermentations.  One fermentation is what I would consider slow to moderate and the second fermentation I would consider vigorous and violent - both fermentations were the exact same grain bill, yeast, mash schedule, boil time, etc.  yet very different fermentations.  Yeast health is the only explanation I can come up with.

I’m curious to read some responses from other brewers.