I can see my beer fermenting, but there are no bubbles in the airlock - why? Inspeck the airlock for a crack in the stem of the airlock. If that is not the problem make sure that stopper or the lid on your container is seated properly. Bucket lids are particularly problematic to thoroughly seal. If you are brewing in a conical fermenter try adjusting the clamp and/or lid gasket.

There are usually a few contributing factors to a violent blow off of your airlock. First is the yeast selection. Certain yeast have a greater propensity to create a "big fluffy head". The yeast that are known for big head productions are White Labs Trappist, WLP300 Hefeweizen, and WLP002 English. Certainly the first two are the most infamous. However, once in awhile we will hear of a yeast like the normally calm WLP001 California busting out of a carboy. A second factor is heat. They yeast go wild when they get hot. Fermentation above 73 degrees are candidates. Another factor is starting gravity. Higher gravity beers have more violent ferments. Sometimes a beer will start to ferment and come to a near halt shortly after starting because of a rapid drop in ambient temperature. When it suddenly becomes warm, because the weather heats up or the carboy is moved to a warmer location, it can cause a yeast breakout. If you plan on brewing with actual fruit in the primary (when lots of sugar are left) you should use a blow off that has a tube inner diameter of at least 1/2". As you can see there is no solid rule for when it will happen but there are certain factors that can be avoided. Don't ferment in a 5 gallon carboy with only an airlock as your primary fermenter. Keep an eye on your fermenter when in doubt.

The beer is fine. When a ferment is going this wildly it is pushing off so much CO2 that no other microrganisms can fall in and contaminate it. Also, the yeast are replicating so fast that if any wild yeast or bacteria fell in most likely it would be consumed by the yeast. Take the airlock and stopper, sanitize and clean them, and reinstall. Have a pint of beer! Trust us you will have many more yeast explosions in your homebrewing career. Something to remember is every yeast ferments differently at unique temperatures.

The question is whether it is better to ferment in a 6.5 gallon carboy or bucket where you have an airlock and there is no blow off versus fermenting in a 5 gallon carboy with a tube attached to the top of the carboy that goes into a jar of water that acts as a blowoff and airlock. With the blow off method most of the krausen gets blown out the top. With the non-blow off method the krausen settles back into the beer after fermentation. In the past homebrewers thought that if you blew this gunk off you would profit from cleaner beer. Some people feel that the blow off beers lose some degree of bitterness, as the oils are lost with the krausen, but it might not matter so much in the long run.