So I went downstairs to get some aspirin and I heard a strange watery hissing sound. Thinking it was a supply hose to the washer I headed to the laundry closet and noticed the nearby bucket about to blow its lid off! A bucket containing 5 gallons of cascade blonde to which I added 6# frozen strawberries and 4# bananas yesterday was hissing away through the drilled stopper holding the airlock... luckily it appears to only be air-tight to a certain pressure.
Naturally I quickly rigged a blow-off tube on and all was good from there (great smells coming out, by the way.) Here are some tips from lessons learned:
1) Put your fruit in a muslin bag or something of the sort. If I hadn't done that there would surely be a huge mess to clean up from a strawberry chunk lodging itself in the airlock opening. Luckily for me it was only the thick krausen partially clogging the airlock.
2) It comes fast! For those of you that think a secondary gets rid of too much yeast... no way, even after being in primary for a month with a week long cold crash. I almost never secondary and the only reason I did this time was to avoid a huge mess but there still seemed to be more than enough yeast. It went from perfectly still with no activity to explosive fermentation four hours later.
3) Use a blow-off tube from the start! Seriously, it'll save you some grief (and some added grief from SWMBO.)