Short Answer: The simplest and most efficient way to ferment at a selected and constant temperature is to use a refrigerator to ferment in. Simply purchasing and using a ‘Fridge Temperature Controller’ to control the fridge and ferment your beer at the temperature you would like. 18-20 degrees is optimal for Ales, whilst 13-14 is optimal for Lagers!
In Depth:
Realise that the following paragraph will contradict what is written in the instructions of most brewing kits (especially Australian ones) where the suggested temperature is often quoted as being in the mid twenties. A maximum of 32 degrees is listed as the upper limit in one well known brewing kit! The yeast will have no difficulty working at these temperatures. In fact it will flourish, fermenting out the beer in rapid-fire time.
Unfortunately, the object of brewing beer is not to ferment out the beer as fast as you can, but to produce beer as good as you possibly can with the equipment and ingredients you have at hand, and to do this you must ferment at lower temperatures.
“Why are lower temperatures better than higher temperatures?”
When yeast is asked to work on brewing wort at higher temperatures (above 25 degrees) it will produce a large amount of fermentation by-products, such as esters and fusel alcohols. These by-products are responsible for all sorts of weird flavours in beer, flavours that are not associated with good beer. Esters produce fruity type flavours in beer, which in low levels can have a positive effect on your beer but start fermenting above 25 degrees and you will finish up with a beer that tastes like tropical fruit punch. This particular problem is most obvious when using a lot of malt and pure brewing yeasts.
The most common problem associated from brewing at high temperatures with kits is the dreaded “Yeast Bite”. This is particularly nasty and once you have encountered it in a brew you won’t forget it in a hurry. It leaves a foul harsh yeasty bitterness in the beer making it undrinkable. This is a problem we see regularly in the shop during the warmer months of the year, and is one which can easily be avoided with a little forethought and planning.
“How do I stop the brew from getting too warm?”
There are several ways to do this, and these are listed below. No doubt you will have some ideas of your own. All of these methods have been tried and tested by our customers or ourselves.
1. Do not use any boiling water to mix all your ingredients, we add two litres of cold water to the fermenter first, add the malts and stir vigorously. You do not need boiling water to mix your malts and sugars a little elbow grease will do the job nicely. By keeping the initial temperature of the brew down you stand a much better chance of maintaining a reasonable temperature. Aim for a pitching temperature of 22 degrees or below. Another thing to consider is that the while the brew is fermenting it will tend to maintain the temperature it was at when fermentation began. This will occur even when the air temperature around it is as much as 4 to 6 degrees lower. For example if the brew starts to ferment at 28 degrees it will tend to stay around this figure even if the air is 22 to 24 degrees.
2. We recommend you freeze some small-sterilized containers of ice and add them to the brew after you have mixed the malt. This will help to get the temperature down, as water from the tap in Cairns is already 26 to 28 degrees.
3. Brew in the coolest part of the house, preferably an area that gets good airflow. Do not brew in your garden shed it is to hot.
4. If you are having difficulty keeping the brew cool try wrapping a wet heavy cover around your fermenter, towels are ideal. All you will need to do is keep the cover wet. As the water evaporates it cools down the fermenter. If you have ever had an alcohol swab applied on your arm you will now how cold it feels. This is because alcohol evaporates very quickly.
5. The method I find easiest to use is to place the whole fermenter into a trough of water. This is very effective, especially if the brew has overheated and you need to cool it quickly. To maintain an even temperature all you need to do is to freeze some water filled 1.25 litre plastic bottles and place them in the trough.
We keep 8 frozen at all times and once the brew is made we place the fermenter in a plastic crate filled with water and add 4 frozen plastic bottles (Coke bottles are great) change the bottles over each morning and night.
6. One final piece of advice. I find it a good idea to reduce the amount of priming sugar you put in your bottles at this time of year to a level teaspoon. This occurs because during the warmer weather the beer carbonates very quickly in the bottle and, if left for several months, will become very gassy.
Good luck!
PS. Don’t forget to put you beer in the fridge as soon as its finished carbonating this will ensure it lagers down nicely.