After 2 days of fermenting, my beer foamed up through the airlock. I was at work and when I got home, there was hardened foam (krausen?) in the airlock. I took off the plug, and some foam shot my in the face! After cleaning out the airlock I attached a blow-off tube, because as soon as the airlock was cleared, it started foaming up through again! Is this vigorous fermentation a good thing? This has never happened before!!!!