Dear Mr. Wizard:
I am brewing a batch of "honey brew" using 6 pounds of amber extract and 2 pounds of honey. I purchased Wyeast 1056 (American Ale yeast) in the 6-ounce size. The package said the yeast was "pitchable" but I stepped it up anyway. Actually, I stepped it up twice: first to about a pint (approximately 1.033 gravity) and two days later to a little less than two-thirds of a quart (1.050 gravity). I brewed everything, cooled it off, and pitched the yeast into my 6.5-gallon carboy.
This is the first time I have used a glass carboy, instead of a 7-gallon bucket. I still chose to use the airlock, never thinking the krauesen would fill the remaining 10 inches of headspace in the carboy. The next morning I got up and found the headspace filled to capacity with krauesen. It was also spewing out of the air lock! Can you step up yeast too much? What are my chances of contamination? I immediately sanitized some hose, a brass coupling and another stopper and set up a blow hose. Your insight would be graciously accepted.
Vance J. Stringham
Mr. Wizard replies:
Although you had a giant mess on your hands with your excited fermentation, you may have added a normal amount of yeast. In my experience, small yeast packets do not contain enough yeast after they swell to contribute a proper pitching rate to a 5-gallon batch of wort. My opinion is based upon observing the vigor of fermentation as well as performing cell counts on yeast from smack-packs with a microscope. Stepping up the pack is a good idea, although one step would have done the trick. My suggestion would be to propagate the yeast in two quarts of 1.048 wort, allow the fermentation to finish, decant the beer above the yeast and pitch the concentrated yeast solids. One to 1.5 cups of yeast solids per 5 gallons of wort is a good pitching rate.
Now the bad news: The krauesen spewing out of your carboy is directly related to your pitching rate. A wimpy rate usually results in a thin krauesen that will rarely leave the fermenter. Air locks can vent the gas from such a fermentation. Increasing your pitching rate increases fermentation rate, decreases certain aroma compounds, decreases the chance of contamination ... and increases the odds of making a mess!
The minimum precaution when fermenting in a carboy is to attach a blow-off hose. Still, I don't think you contaminated your beer by neglecting to use a hose. Any microscopic invaders were most likely pushed onto your floor along with the krauesen. Usually the headspace provided by a 6.5-gallon carboy is plenty for a 5-gallon fermentation, but sometimes foam happens!
Mr. Wizard, BYO's resident expert, is a leading authority in homebrewing whose identity, like the identity of all superheroes, must be kept confidential. To see more of Mr. Wizard, check out the latest issue of Brew Your Own at better homebrew shops and newstand locations.