An Airlock isn’t a great tool for monitoring fermentation. Temperature changes, dry hopping, and settling of yeast can all cause an airlock to bubble – none of these are indicators of fermentation. The only way to be sure a fermentation is progressing is to monitor the SPECIFIC GRAVITY with a hydrometer. Not only will this help you to work out the alcohol-by-volume (abv) of your beer, it will also show you definitively that your beer has finished fermenting and is ready to be packaged. Monitor the specific gravity of your brew with a hydrometer and bottle/keg your beer when it is stable (no change) over 24-48hrs
If you are using a hydrometer and you do not notice any yeast activity or change in specific gravity, make sure of the following:
You’ve fermented within your yeast’s temperature range,You’ve used enough yeast (we recommend 2 or more sachets for worts over 1.050 OG)Your wort is fermentable. Worts with a very low pH, with excessive adjuncts, a high proportion of dark malts, or mashed too hot may all struggle to ferment.
We also recommend to pick up your fermenter with the side handle, give it a gentle swirl. This will help to stir up the yeast which may give some activity in the airlock after 24 hours (do not open the lid)