why a really late near boil over


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Aug 28, 2013
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So I was boiling my wort last night on what is to be my fifth batch of homebrew. This is a smaller test batch, meant for a 2 gallon fermenter. I started with 2 gallons of water, steeped my grains and some pumpkin for 30 minutes, removed the grains, added 2.65 pounds of LME and brought to a boil. Waited for the hot break and added 0.6 ounces of Hallertau and set the timer for 60 minutes. Everything was going fine until about 9 minutes left in the boil when what looked like another hot break was happening, only this time, with only a little more than a gallon of volume left in the kettle, it foamed up to nearly fill my 5 gallon kettle. I stirred it back down and lowered the heat a tad to get it under control and finished out the hour. Any guesses what caused this and what the result may be?
Did you use a Whirlfloc tab? I nearly had a boil-over last weekend because of it - it really makes the wort foam up for a few seconds. Another possibility: Did you do a late hops addition? Hops, particularly pellet hops, cause foaming. One thing that bites me from time to time is using my propane burner outside on a windy day - the wind can disperse the flame and if it becomes calm, heat the kettle too hot and cause a boil-over. Lots of possible causes but to diagnose, we'll have to know pretty much exactly what you did, added, etc.
:( I told you what I did and when. All of it. Unless you want a diary of my stirring motions. . . ;)
Maybe the pumpkin caramelized or something landed in the kettle??
Like Larry, I was looking for some addition to the wort, advertent or otherwise, to cause this. About the only other thing I can think of apart from some addition to the kettle either releasing heat or providing nuclei for boiling is some sudden increase in heat.