Lager Fermentation: Keeping It Cool

lager fermentation

Brewing lagers at home can be a bit daunting. There’s lots of information out there about how challenging lager fermentation can be, and truth be told it may require some new skills and new equipment. Lagers can be seen as something of a mystery, but this article is here to explain the basics, and potentially give a head start to anyone considering brewing their first lager. Come, let us explore…

Some Basics

Beer doesn’t need to be complicated. Despite the dizzying array of beer styles available today, there are really only two different kinds of beers – lagers and ales (yes, I realise there are exceptions). And there’s only really one major difference between these two beer styles – the yeast. Both are fermented with Saccharomyces Cerevisiae, but lagers are made with a sub-strain called Saccharomyces Cerevisiae var Pastorianus. These different yeasts have different preferences, and this affects how a brewer must manage the fermentation.

The Lager Fermentation

Unlike ale yeast, lager yeast prefers cooler temperatures, usually in the range of 8-12 degrees Celsius. This can present a challenge to home brewers, as this temperature range is below the usual ambient temperature (at least in Australia!), but is above the range of a normal refrigerator. To get around this, most lager brewers build a temperature-controlled fermentation chamber. This is easily done with an old fridge and a temperature controller, but of course space and electricity consumption are issues to consider. Another option is to put the fermenter into a water bath and add ice to keep the temperature down. This usually requires a lot of monitoring, and can also be unreliable. But it does work well to keep the fermentation temperature in the correct range.

Since lager yeast prefers cooler temperatures, it tends to work slower than ale yeast. Cooler temperature means slower metabolism, which in turn means more time is taken to convert sugar into alcohol. This is overcome by pitching a much larger quantity of yeast than would be used for an ale fermentation. This reduces the need for the yeast to replicate and allows the lager fermentation to begin quickly. Home brewers should really make a starter for the yeast when brewing lagers to ensure a healthy fermentation.


The word lager is derived from the German word lager, which means ‘storeroom.’ Lagers were traditionally brewed in the cooler months, and stored underground in caves until ready for consumption. This allowed the yeast even more time to work to reprocess any fermentation by-products, and to consume any remaining sugars. The result was a crisp flavoured, dry beer with a very clean fermentation character. People clearly found this delicious, and so the tradition was continued to the modern day. Modern lagering is performed at near-freezing temperatures, from -2 to 4 degrees Celsius (remember, alcohol has a lower freezing point than water!). As well as allowing the yeast to slowly continue to work, it also causes suspended particles and yeast to stick together and drop to the bottom of the fermenter. This creates a very clear beer. So once lagering is over the brewer is left with a clear, crisp and dry finished beer. Excellent!

Considerations For Home Brewers

Lagers certainly require more effort to produce than ales, and unfortunately this tends to mean that home brewers avoid them. They can also be quite unforgiving of mistakes, especially pale lagers. I can’t count how many pale lagers I made that tasted like apples until I finally mastered the technique. There are a few important things to keep in mind if you want to try making a lager at home. Firstly, pitch more yeast. At least twice as much as you would use for an ale, if not more. I save the yeast from previous batches and reuse it. This not only saves money but also means the yeast is healthy and functioning well. Another option is to make a yeast starter, which is essentially a small batch of beer anyway. Secondly, temperature control is very, very important. Lager yeast can produce horrible flavours if it gets too hot, and these flavours can leave a beer undrinkable. Keep the temperature below 13 degrees Celsius at least until fermentation is almost over. Finally, to produce a true lager, the beer needs to be put into cold storage for at least a few weeks after fermentation. I lager at 2 degrees Celsius for at least a month, and longer is better if you can wait! I find lagers are usually at their best after around 2 months of cold storage.

Brewing lagers at home can be challenging – they require a lot of patience and persistence. But keep in mind that tackling lagers can take a home brewer’s skill level up a few notches very quickly!

If you have any questions or comments please leave them below, thanks for reading!


Leave a Reply

Your email address will not be published. Required fields are marked *