Is my beer fermenting?

How do I know when or if my beer is fermenting?

Sometimes it is extremely difficult to determine if your brew has been fermenting or has even started fermenting at all.

After pitching your yeast, fermentation will typically take about 6 to 18 hours to start depending on the age of the yeast or if you have made a yeast starter prior to pitching, so don’t worry if it takes a little while to get started. During this time nothing will appear to be happening, however, the yeast is preparing to ferment by making the necessary enzymes and reproducing.

The first signs of fermentation will be wisps of foam starting to form on the surface of the brew and these will get bigger and eventually join up to form a layer of foam on top of the brew. Another sign of fermentation is the formation of yeast building up on the base of the fermenter which is a good indication that the yeast has been reproducing. Also, another indication of fermentation is the brownish scummy ring that forms around the top of the brew.

If the airlock is not bubbling, but you can see any of these indications above then your brew is or has finished fermenting. All it means is that your fermenter is not sealing properly, though this is nothing to worry about. If it has been some time since you pitched the yeast and fermentation appears not to have started then take a hydrometer reading. If the reading is a lot less than your initial reading then fermentation is probably close to being finished.

For example; if your OG is 1050 and your FG is 1010, then your brew has been fermenting.

Depending on the type of yeast that you use will also determine the time that it takes to ferment. If the temperatures are fairly high then fermentation will be quicker, however you want to try and avoid going over temperatures above 27°C as this will start to produce off flavours that can spoil you brew. Most ale yeast is ideally brewed between 15°C – 26°C for a period of 7-10 days, while lager yeast has ideal brewing temperatures of 11°C – 15°C over 2 – 3 weeks. If you can maintain such temperatures then this will add to the quality of your beer overall.

If the hydrometer reading is the same then fermentation has not started from your OG then you may have killed the yeast by adding it when the wort was too hot, or the yeast may have been old and unhealthy. Dried yeast has a shelf life of 18 to 24 months and needs to be stored in a cool place. If fermentation has not started after several days, then taste a sample of the wort. If it tastes OK then add another sachet of yeast. It is a good idea to always have a couple of spare sachets of yeast on hand.

Ultimately the best way to determine if your beer has been fermenting or not is to use your hydrometer, it is always good practice to take notes on what you have been making and keeping track of your gravity readings. That way if you want to reproduce the same beer in the future you will have a good indication on what to expect.