I almost learned my lesson the hard way this weekend. I have thought about using a blow-off tube in the past as I've had airlocks fill with krausen, but this was just not good. If you think adding a blow-off tube is hard, it's not. The picture immediately below was posted by Revvy in 2009 and shows what I *should* have done. Instead I ended up with the scary picture even further down - this was a beer with only a 1.050 OG (though was using Weihenstephan yeast).
Always, always use a blow-off tube!
Always, always use a blow-off tube!