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...