How Long Does It Take For Beer To Ferment?

Fermenting you beer is the process of turning from a simple sugary liquid into the final product

So, how long does it take for beer to ferment? The answer varies depending on a number of factors, including your yeast, your ingredients and the temperature – but it’s safe to assume that fermentation will take at least 2 weeks before you can start the process of packaging your beer.

How long should fermentation take?

Depending on your yeast, you can expect the whole process of fermentation to take around 2 weeks from pitching the yeast to being in a position to package your beer.

Primary Fermentation Time

Often you’ll find that the bulk of fermentation will actually take place between days 2 and 8 of the process, where the bubbling is at its peak. The rest of the time is spent by the yeast cleaning up the product, absorbing any off-flavours produced during the process and creating a brighter looking product.

While it’s tempting to package the beer as soon as the bubbling has finished my advice would be to wait the full two weeks to allow the yeast to complete the cycle and drop to the bottom of the tank.

Trust me, your beer will be better for it.

If you are only fermenting in a single vessel, then you can bottle or keg after two weeks, however if you are planning on using a secondary fermenter – then it’s a good idea to transfer your beer around day 12.

Secondary Fermentation Time

Secondary fermentation is an optional process performed at the end of primary fermentation where you rack the beer into a second container. By removing the beer from the spent yeast you can greatly reduce the risk of the beer developing off flavours.

Most modern yeasts have been engineered so that secondary fermentation isn’t required but it’s probably a good idea if you are planning on aging your beer before packaging.

If you plan on using secondary fermentation then i’d leave it for a minimum of 2 days before bottling your beer to allow any sediment to settle out.

What happens if fermentation doesn’t start?

Typically fermentation should start within 24 hour of pitching – you should notice some bubbling through the airlock or blow-off tube, increasing in frequency over the next few days.

Occasionally you may notice a delay in this process starting – this is fairly normal, be patient, you should see some activity within 48 hours of pitching.

If you get past 48 hours and still don’t see any activity from the yeast then something has probably gone wrong. Some of the reasons could be:

  • Pitching temperature was too high
  • Not enough yeast
  • Out of date, non-viable yeast.

Pitching Temperature Too High

Yeast is highly sensitive to temperature and from experience needs to be pitched when the wort at 25 degrees celsius (77 degrees fahrenheit) or less. If you’ve pitched at a higher temperature then its possible you’ve either killed the yeast of at the least impeded its ability to work properly.

In this case i’d probably try pitching another packet of yeast into the wort – this should kickstart the process.

Chalk it up to experience and be a bit more aware of your pitching temperatures for your next brew.

Not Enough Yeast

Under pitching of yeast is a common problem with fermentation not starting as expected. Taking US-05 as an example, the recommended pitching rate is one 10g packet per 5 gallon batch.

If you are brewing 10 gallons then you’d either need to pitch a second sachet or create a yeast starter.

If you underpitch yeast then fermentation will start eventually, but you may develop off flavours due to the yeast being stressed or overworked during fermentation.

Out of Date Yeast

Yeast, like most other foodstuffs has a use by date and decreases in viability over time. If you use yeast that’s either close to or past its use by date then you risk fermentation not starting.

Make sure you use fresh yeast and check the dates when you buy and plan your brews accordingly.

What are the signs that fermentation has finished?

Typically you can assume that fermentation has finished a couple of days after the bubbling has stopped. At this point the krausen should have dropped to the bottom of the fermenter and the beer started to clean up.

How to test that fermentation has finished.

The most accurate way to confirm that fermentation has finished is to take a couple of gravity readings a few days apart. If you continue to see a drop in the final gravity, then you know that fermentation has yet to finish.

If you find that the gravity readings are unchanged over a couple of days then you can safely assume that the beer is now done.

Note: This article was originally written for a collaborative brewing project that never got off the ground so i’ve decided to post it here.

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