The ‘How to All Grain Homebrew Series’: #5 Fermentation

Temp Controller

For those who haven’t read my blog before, the ‘How to All Grain Homebrew Series’ gives a basic run down of the all grain brewing process. By no means is this an exhaustive description of the process but does set down a basic structure to allow the reader to have a bit more context of the brewing process.

I find when people ask about homebrewing, they want this kind of high level overview of what you do to make a brew. In later posts, I will likely explore each element in a lot more detail. Today we are going to talk about what is likely the most important part of the process, fermentation.

If you read enough beer blogs, you will come to see the same wanky bits of advice pulled out time and time again. One particularly wanky comment I see all the time is ‘Brewers create wort, yeast create beer’ or something similar. Whilst my first reaction is ‘Cool Story Bro’, this comment does highlight that this is the part of the process where you give up control of making the beer.

For those who don’t know, fermentation is the process of allowing yeast to consume the sugars in your beer and create alcohol. Not only does yeast create alcohol it creates a number of by-products which contribute to the taste of your beer. Different yeasts give off different qualities and are therefore are used for different styles of beer. This is why beers can taste so unique even though they are made with similar ingredients.

Different varieties of yeast prefer different environmental conditions to create a preferred taste. Generally ales will range from about 16 degrees Celsius to 28 degrees Celsius and lagers will be in the late single digits/early teens. Living in Queensland, we experience the perfect temperature for about 15 seconds of the year, so I would highly recommend you use a fridge and temperature controller to ensure that the yeast maintain the temperature you want. Too cold and the yeast will go dormant and struggle to perform, too hot and the yeast will perform too well and throw off a lot of off flavours.


Yeast also require oxygen to ensure a strong fermentation and this can be achieved in a number of ways. The most popular (because it is the cheapest) is to splash and shake the wort and introduce oxygen in this way. There is a lot of conflicting information about how effective this method is but it is generally accepted that the best you can achieve is about 8ppm. How much oxygen you need depends on the Original Gravity of the beer but I find that this method seems to be sufficiently effective for your usual full strength beer. Where you start to run into trouble is with ‘Imperial’ beers of 8% or above and with lagers.

If you have one of these beers, it may be worth trying an oxygenation system (which simply puts air into the fermenter) or pure oxygen. I haven’t tried either so at this stage can’t really give you any recommendations. I am interested however in giving the oxygenation system a go and will do a post if I go down this path.

The final variable relates to the size and activity of your yeast pitch. I tend to use dry yeast a lot and pitch it far heavier than recommended. My readings have suggested at the homebrew level, it is very unlikely to overpitch whereas it is quite easy to underpitch. I’ll generally rehydrate 2 x 12g packs and pitch into a usual full strength beer.

If you are using a liquid yeast, it is generally recommended you do a starter and I will discuss this in another post.

Fermentation usually lasts about a week but the only way to know is by doing a hydrometer test. If the same FG is recorded over a couple of days, the beer is likely finished. It is generally recommended that you err on the side of caution and give the brew a couple more days even once its reached FG. In most instances, I will wait 2 weeks before I start doing gravity tests. From here I will generally ‘crash chill’ the beer which involves putting the refrigerator on full blast to drop out all of the material in the fermenter.

I will finally add a fining agent such as Gelatin before kegging or bottling. Sometimes I doubt how effective this is but tend to do it simply because Gelatin is so cheap and it adds very little time or complexity to the process.

Fermentation is probably the most important stage of the beer brewing process. It is the time you present up your wort and hope the yeast does what you want them to do. If all goes to plan, you are far closer to drinking that delicious, delicious beer that is waiting for you.

Feel free to post your questions below.


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