Ask Dr. Beermeister

Q: When I do my primary fermentation in a glass carboy with a bow-off
   tube, sometimes I get lots of blow off and other times very little. Why
   the difference? How long should I wait before adding the dry hops?

A: The two biggest causes for variation in blow off are temperature and
   yeast. At warmer temperatures yeast is more vigorous and produces the CO2
   faster, causing more blow off. I tend to leave a larger head space in the
   carboy for my summer brews. Different strains of yeast ferment at different
   speeds, again causing variation in the foaming during fermentation.
   Another, smaller factor is that heavily hopped beers have better head
   retention, both in the fermentor and in the final poured glass of beer. The
   next time you make a hoppy beer, note how many rinses of your carboy it
   takes before the rinse water is no longer foamy. Add the dry hops after
   the head has fallen and three to seven days before you bottle.


Q: What is the perfect temperature for fermenting ales? Lagers? What kinds
   of things can I do to help achieve the perfect temperature without spending
   lots of money on refrigerators, etc.?

A: There is no "perfect" temperature. Different breweries use different
   yeasts under different conditions to produce a wide variety of beers. Most
   breweries ferment ales between 60 and 70 F. The lower temperatures are
   preferred by breweries that want to emphasize the malt and hops rather than
   the yeast characteristics like fruity and estery aromas. Others that use a
   special yeast to produce special characteristics (like some Belgian beers)
   sometimes ferment between 70 and 75 F. I have talked to a homebrewer from
   Tucson, AZ, who successfully brewed ales in the summer at 90 F by being
   extra careful about sanitation. He could make a good drinkable beer at
   these temperatures using pure cultured yeasts, but not with dry yeasts.
   The primary fermentation of lagers is usually done near 50 F. Then in the
   secondary stage the temperature is dropped to the low 40's. During long
   term aging, the temperature is near freezing. Whole chapters of books
   are written on the temperature variations used to make lagers. I highly
   recommend that you read more about this subject before trying to make a
   traditional lager.

   If you have a basement, it is probably the right temperature for ales all
   year. If you don't, putting your carboy in a tub of water and covering the
   carboy with a towel or T-shirt dangling in the water will keep your beer
   several degrees cooler in the summer. Some people even use a small electric
   fan to blow on the carboy to enhance the evaporative cooling. Traditional
   lagers are really hard to make without good temperature controls. "Steam"
   beers are made with lager yeasts at ale temperatures; therefore, they
   have more of the ale style of characteristics. Try making clean ales at
   as low of temperature as you can achieve. That might satisfy your craving
   for a homebrewed lager.