Yesterday I brewed my third extract batch since returning to homebrewing. For the first two, I had to keep adding water to the airlock during the first few days of fermentation. To avoid that, I decided to use the blowoff tube and switch to an airlock after the heavy bubbling was over.
All three of the kits are Northern Brewer. The first two were the Nut Brown Ale and the Honey Brown Ale. Neither one came close to hitting the top of the 6.5 gallon carboy. In fact each one barely had over an inch of foam before it settled out.
This time I did the Caribou Slobber, and slobber is an understatement! There was an inch of foam on the surface when I checked it this morning. When I got home from work, the carboy was completely full of foam and it's starting to work its way into the hose. I expected more activity than the first two kits from the extra pound of dry malt extract, but this is impressive. I'm really glad I used the blowoff tube with it!