Primary blew its top!! Normal fermentation activity

I have a 6.5g bucket and a recipe for 5 gal. I decided to add some extra malt to bring it to 6 gallons (mistake) Anyway, a day later it had foamed up enough to clog the air lock and blow the top. I cleaned the lid and airlock and replaced it, noticing that the foaming had dropped to about 4 inches from the lid. I assumed that the violent initial fermentation was over since the foam was subsiding. After the lid was replaced for about 2 hours, i noticed discoloration in the airlock water and removed the lid. Sure enough, it had foamed back up to the top again. I set the lid back on without sealing it to avoid another small explosion.

My question is, why did it foam up a second time? I assumed it foamed up alot in the beginning b/c the yeast is all excided with the sugar and what not, but once the foam dropped, i assumed it was slowing down. Does it ferment in stages? Does the lid being off slow it down? What gives? I would assume that since it had a day to produce alcohol before being exposed to the open air, the chance of contamination is much less; is this the case??

blow off tubes are your friend!

not if the blow off tube gets clogged

Actually, fermentation can run in stages as the yeast adapts to sugar complexity. A double blow-off is unusual.

possibly because the yeastys got more oxygen?

I'd think that since you took the lid off, less back pressure and easily vented wort. When you put the lid back on, you sealed it up again. It was still brewing inside, you just didn't notice it as much.

thanks guys, it seems to have settled down now, talk about a batch of brew with an attitude problem

I use a 1" blow off tube and i've never had a clogged tube yet?

Done that in an apartment once. The wife never has forgiven me. Make sure that your overflow tube is in place but not pushed in too far. It needs to be only about 3/4 of the way into the stopper.