I said I'd be back with new homebrewing definitions and this situation brings on some very colorful vocabulary.
Let me set the scene. You've just poured a batch of must into a carboy to ferment and gone off to do something else, like write articles on Blogger. When you return to your brewery some time later, you discover that the fermenting process has knocked the airlock off the top of the carboy and spilled a peach concoction all over the kitchen floor. Yeah, that just happened to me.
Sometimes yeast gets very active and the wort or must can expand in the early hours of fermentation. It's a desired effect in its own way but it works better for rising bread than brewing beer, wine, or mead. It signals that fermentation is happening and the yeast are awake and getting down to work.
There are a few methods for dealing with blow off. To start with, leave some head space in the carboy. Don't fill it too full with wort or must. That will leave the brew some room to expand into before reaching the airlock. Experience will tell you where the fill line is for a particular recipe in your equipment. Additionally, most carboys come with both an airlock and blow off tubing. To use the tubing, sanitize it with the rest of your brewery gear and install one end in the stopper in place of the airlock and sink the other end under water. A reserve of sanitizing solution can be held back for this purpose or plain tap water can be used. You just need to ensure that the hose acts like the airlock and only allows CO2 out, keeping out air and foreign bacteria.
Within a few days, the yeast will settle down and won't be forcing any more material out through the hose. You can replace the hose with the airlock assembly at this point. Good luck!
Please drink responsibly.
