Temperature is as important a variable as yeast pitch rate, fermentation pH, and time. A consistent fermentation temperature keeps your yeast happy and healthy. At different temperatures yeast will ferment at different rates and create different chemical compounds while they eat. Having large swings in temperature will cause the yeast to go through phases of slowing down or stopping and eating too fast, all of which are unhealthy and less than predictable.


By maintaining a specific temperature we can make sure that the yeast make the flavors we expect and want and that they fermentation finishes completely in a reasonable time frame. 




Methods to monitor your fermentation temperature

  • Analog thermometers
    • There are stick on thermometers, glass thermometers, and analog dial thermometers that can be affixed or inserted in fermenters to read the temperature on demand.
  • Electronic temperature controllers
    • These are devices which read the temperature of your fermenter from the inside with a temperature probe usually submerged in a thermowell. Your temperature modifying device is then plugged into the controller, and when the controller senses the temperature going out of range, it will turn on or off your coolant pump or your heater.
  • Wireless and logging thermometers
    • Devices like the RAPT Pill float inside your fermenter and continuously monitor the fermentation temperature and record it to an app. These are super handy for charting your entire fermentation and understanding, in real time, how your yeast are doing. 




Fermentation Temperature Control Methods

  • The Fermentation Chamber
    • An insulated box, insulated bag, cold cellar, or refrigerator can be used to maintain a specific temperature for fermentation. Even if you do not have any way to change the temperature inside of the chamber, the consistency of the temperature will make your fermentation more predictable.
  • The Bath
    • Using a water bath can be a very easy way to maintain temperature control and adjust temperature. You can submerge your entire fermenter in a bath tub or large bin of water, then add ice packs, frozen water bottles, or warm water to adjust your temperature as needed.
  • The Jacket
    • Stainless Steel fermenters and storage tanks are often sold with a "Jacket". This is a second layer of stainless steel that allows you to flow coolant from a "Chiller" around the outside of the fermenter. This basically the same as "The Bath" listed above, but much higher tech. 
  • Immersion chilling
    • There are now stainless steel coils that can be submerged through a wide lid in a fermenter. The Fermzilla for instance has an optional lid specifically built for one of these coils. Coolant or cold water is pumped through this coil, straight to the heart of the fermentation to help keep everything cool and consistent. 
  • Fermentation heaters
    • There are different ways to heat a fermentation from exterior fermentation bands and wraps to immersion heaters. These are most helpful if you live in a cold place and can rely on the ambient temperature of a garage or cellar to cool the fermentation for you. Then you simply need to add a tiny bit of heat to make sure the yeast never stall.



Overall the method of fermentation control and level of technology will depend a lot on your budget and space allowed for brewing. Historically beer makers would brew different styles of beer with different yeast depending on the seasons' weather. In cold months you can more easily brew lagers and in hot months you can brew with Belgian or Kveik yeast. Nowadays if you can afford and store some extra equipment you can enjoy brewing any beer style any time.