I brewed my second batch yesterday, Brewers best Calif imperial pale ale. I expected a healthy fermentation because of all the fermentables in it. I aerated the hell out of the wort, rehydrated the yeast, and let it go.
At three hours post pitch, I could already see krausen starting to form. At 6 hours I had a good 1/4 inch of krausen.
I got up this morning, and checked the brew closet. My airlock was filled with Krausen, and it was leaking all over the place. This was only 15 hours after pitch! I hastily sanitized a new stopper, and some hose, and made a quick blow off tube. The sounds of the gurgles made me smile all day.
I don't have a dedicated full size blow off tube, but my next order is going to include one for sure.