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Keep It Warm

There are certain circumstances in which you may want to raise the fermentation temperature.

Dave Carpenter May 13, 2014

Keep It Warm Primary Image

In a previous post, we discussed options for lowering the temperature of an active fermentation. Because the fermentation process produces heat, homebrewers are far more likely to need to cool down a vessel of homebrew than warm it up.

  • Brewers who ferment in a basement or garage may find that the ambient temperature is too cold.
  • Some fermentation profiles incorporate a gradual temperature rise, for example, from 65 to 75°F (18 to 24°C) over the course of seven days.
  • Certain yeast strains and bacterial cultures benefit from elevated temperatures. Classic saison strains, for example, may require temperatures as high as 95°F (35°C) to achieve full attenuation.

If you find that your fermentation could benefit from a little extra warmth, here are a few ways to bring the heat:

  • Blanket or sleeping bag: This low-tech solution relies on the natural heat generated during fermentation. The trick is to insulate your fermentor when you think the peak temperature has been reached. Adding insulation too early could warm things up more than you’d like.
  • Heated belt: Specialized heating jackets that wrap around a carboy are available at many homebrew stores. These usually supply very gentle warmth and may be used alone or with a temperature controller.
  • Seed mats: Seed mats are used to sprout seedlings indoors and give them a head start on the growing season before being transplanted outside. A seed mat is similar to a dedicated heat belt, but because it’s designed to lie flat, such a mat is best placed beneath the carboy.
  • Light bulb: A light bulb placed in an insulated chamber can supply enough heat to keep the temperature several degrees above ambient. Using a light bulb and chest freezer together with a dual-stage controller, the handy homebrewer can build a fermentation chamber that maintains temperatures to within a couple of degrees of a desired setpoint. Just don’t place the bulb next to anything flammable!

Good temperature control is a critical step toward brewing world-class beer at home. When you can reliably maintain yeast within its ideal temperature range, your homebrew will take a giant step in quality and consistency. Brew on!