An important part of the process of how to make beer is fermentation. This is when your wort becomes beer. One of the most important factors of fermentation is the temperature at which your beer ferments. It is important to maintain a consistent temperature within the ideal range. The appropriate fermentation temperature varies, and will depend on the strain of yeast used. Usually, yeast manufacturers will put the optimal fermentation temperature on the package.
Generally speaking, ales ferment between 60 and 70 degrees while lagers ferment between 50 and 60 degrees. Fermenting at too low a temperature can result is a stuck fermentation, which is a literal stoppage of fermentation before it is complete. This causes the yeast to go dormant, or it can even kill the yeast, prior to all the sugars being converted. If you try to bottle beer that isn’t completely fermented, you can wind up with bottle bombs. At the very least, your beer probably won’t taste too good. If you ferment at too high a temperature, off flavors will occur due to the production of esters.
Esters are undesirable compounds created by the yeast and produce bad fruit flavor in your beer, usually a banana flavor.
High temperatures also encourage the production of fusel alcohols – heavier alcohols that can have harsh solvent-like flavors. It is also important that the proper temperature is maintained steadily throughout fermentation, as opposed to wildly fluctuating.
A common mistake that homebrewers make is pitching the yeast when the wort has not been chilled enough, and is still relatively warm. If the wort is too warm when the yeast is pitched and slowly cools to room temperature during primary fermentation, more diacetyl will be produced in the early stages than the yeast can reabsorb during the secondary stage.
There are many methods to maintaining the proper temperature range during fermentation, but it is important to find what works best for your situation. Where you live (climate) plays a big factor in temperature control, as does the time of year (season).
Obviously, during colder months it will be necessary to keep the beer warm, and in warmer months you will need to cool the beer.
If you have a closet, basement, or some room in your house that is cooler, this is the easiest solution for fermenting. You can even buy a fridge or freezer especially for this purpose. If you are just starting to learn how to make beer, you probably aren’t likely to make that kind of investment at first, but there are several cheap ways to maintain proper temperatures, and a couple of do it yourself projects you can try as well.
The cheapest and easiest method is simply being able to rely on the ambient temperature inside your home—the a/c or heating maintaining a constant temperature inside. Obviously, this may not work for everyone, or at least not year round.
A water bath can be one easy solution. Simply place your bucket or carboy in a bathtub and fill with water (you will want to use a guest bathroom tub for this). Or, you can place it in a kiddie pool or rubber tub. If necessary, you add ice to it to help cool it. This is known as a “swamp cooler”. The best way is to take some 2 liter soda bottles and fill with water—alternatively, you could use Tupperware containers as well, or fill ziplock bags—and place them in the freezer. Once frozen, simply put into the water. If temperatures are hot enough, it may be necessary to change out the ice a couple times a day to maintain the temperature.
You can also wrap your fermenter with a wet towel or t shirt to help cool. In addition, you can point a blowing fan onto the fermenter, and this will help cool as well.
You can go all out and purchase a refrigerator or freezer specifically for fermentation. If you or a friend has an old fridge or freezer lying around, then this is a great option. You can also search for second hand fridges/freezers at local second hand stores, or look for slightly damaged ones at home supply/appliance stores. Look online at places like craigslist or ebay. You will need a separate temperature control device, but these are easy to find and aren’t that expensive.
Many home brew supply shops carry these controllers for home use.
You may even be able to find a fridge/freezer available that has already been converted from another home brewer. This option doesn’t necessarily have to be an expensive one.
Another option and another do it yourself project is what is known as a son of a fermentation chiller. There are many variations on this, but you are basically making a separate storage place for fermenting (much like a fridge or freezer) that you can control the temperature—basically, a big box for fermenting.
What’s great about these options is there are many do it yourself projects out there, that range from very ghetto set ups to some very nice set ups.
I’ve even seen someone that made a fermentation chiller out of cardboard that they glued together and lined with some fiberglass insulation. They went with frozen 2 liter soda bottles, and this set up worked just fine for a total cost of $13.
Just keep in mind, there are many ways to accomplish temperature control when fermenting. This is a great topic to research online and at home brewing forums, because you will see many different ways home brewers accomplish this. You will find many different set ups that might make for some great do it yourself (and cheap) projects.
One thing that is important to note about fermentation temperatures. The Fermentation process itself will produce heat, so whatever the ambient temperature is surrounding your fermenter, likely the beer inside is a few degrees warmer. There are thermometers and probes you can purchase to monitor the actual temperature of your beer during fermentation.
Many brewers notice an improvement in their beers when they have made extra efforts in maintaining the fermentation temperature. Buying some sort of mechanism that actually maintains the beers temperature, and not just the ambient temperature, is something that isn’t necessary when you are first learning how to make beer, but could very well be worth the investment as you dive further into this hobby.