Today we’ll take a look at a homebrewing technique called the “blow-off method” or Burton Union System for improving your beer. The blow-off method removes proteins, tannins, grain husks, hops and other undesirable materials that tend to form at the top of the fermenter during the early stages of active fermentation.
These materials are an undesirable byproduct of the brewing process, and float or get pushed to the top of the fermenter by carbon dioxide produced during the active stage of fermentation. These undesirables form a separate layer, called the ‘Kraeusen’ over the beer.
We wish to separate these from the beer as early as possible because tannins, proteins, and other materials will contribute to cloudiness as well as add off-flavors to the beer. Many people use a secondary fermentation or conical fermenters to separate the beer from heavy materials that fall out right after active fermentation. The blow-off method attempts to remove lighter materials that float to the top of the fermenter as early as possible.
I first read about the blow-off method in Charlie Papazian’s book “The Home Brewer’s Companion” (p 172), and have used it successfully for the last 15+ years. Commercial brewers in Burton-on-Trent pioneered the related Burton Union “blow-off” system over 200 years ago and have used it for popular styles like Bass Ale. Their system recovers some of the flocculent yeast from the top fermenting ale and reuses it for later batches. However, the blow-off method used by homebrewers merely discards the kraeusen.
To use the blow-off method, you need a glass or plastic bottle fermenter of the same size as your target volume. A 5 gallon glass carboy is ideal. Next, procure several feet of 1″ inner diameter plastic tubing. The tubing should fit tightly in the top of the carboy.
The method, as shown in the picture above, is to fill the carboy to the top when brewing and then use the large size tube to “blow off” the early foam and material that rises during active fermentation. A large container with water captures the liquid and material blown out of the fermenter and also acts as a giant airlock. Obviously you should use a much larger container for the overflow than shown in the picture, and also you should partially fill the container with water so the end of the tube can be kept under water forming an airlock seal.
Leave this system in place for active fermentation during the first few days, and switch to a smaller airlock or secondary fermenter once activity has died down. You do need to be careful, however, as a smaller airlock will clog up if active fermentation is still ongoing. On one occasion, I switched the airlock before fermentation had completed and ended up blowing the stopper and airlock right off the top of the carboy. It was a huge mess.
If you have a suitable 5 gallon carboy, give the blow-off method a try. You will be surprised how much debris collects in your overflow tank and not in your beer. I’ve been using this method since the early 1990’s with great results.
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