How to Know When Homebrew Is Done Fermenting

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Fermentation is the most critical step in the homebrewing process. When the yeast you used starts turning the sugar into carbon dioxide.

It’s critically important to remove the homebrew from the fermenter once it has done fermenting. Otherwise, it can lead to a process known as autolysis, which refers to the self-destruction of homebrew.

In this article, I’ll discuss how to know when homebrew is done fermenting so that you can start adding it to bottles or a keg.

How to Know When Homebrew Is Done Fermenting

Fermentation is what converts the wort into homebrew. During this process, yeast produces alcohol and carbon by consuming sugar in the wort. The duration of fermentation depends on the homebrew recipe you’re following. You can use the following methods to know when your homebrew is done fermenting.

Using a Hydrometer

The easiest and most efficient way to know if your homebrew is done fermenting is to use a hydrometer. It’s a tool that allows you to determine the relative density of liquids. Use the following steps to use a hydrometer to find out if your homebrew is done fermenting.

Step 1: Extract a Sample

Extract a sample of your cooled wort before pitching the yeast. While you can use your brew to take the reading directly, I recommend retrieving a sample from the homebrewing system. It’ll minimize the risk of contamination that can ruin your entire batch. You can use a beer/wine thief to extract a sample of your wort.

Step 2: Check the Calibration

To use a hydrometer at a particular homebrew fermentation temperature, you must calibrate it first. This temperature usually ranges from 60 to 65 degrees Fahrenheit. However, you can read the instructions mentioned on the hydrometer’s packaging to find the exact temperature.

To calibrate a hydrometer, pour distilled water into the test jar at the recommended temperature. Place the hydrometer in the water gently and make sure it starts floating vertically without touching the sides. The line to which the distilled water rises is the gravity reading you need to record.

If the gravity reading is 1.000, your hydrometer is perfectly calibrated. However, if you get a different reading, you’ll need to use any of the following techniques:

  • If the reading is more than 1.000, you’ll need to subtract it from the reading that you get from your wort sample. 
  • If the reading is less than 1.000, you’ll need to add it to the wort sample reading.

Step 3: Record the Original Gravity

Before taking the original gravity, I recommend you sanitize your hydrometer. It’ll ensure that you get the right reading for the OG (Original Gravity). Use the beer/wine thief to transfer the sample you took earlier to the test jar of the hydrometer.

Make sure the hydrometer isn’t touching the sides of the jar and record the reading of the line to which the sample rises. It’ll be your original gravity.

Important Note: The ideal temperature of the work should be around 60 degrees Fahrenheit while measuring the value of original gravity. If the temperature of your wart differs significantly, use a hydrometer temperature adjustment calculator or chart to adjust the value of the OG reading.

Step 4: Record Final Gravity

The recipe will indicate the recommended fermentation time. Once that time has passed, take a sample from the fermenter using the beer thief and pour it into the test jar. Use the same technique to get the value of the final gravity and write it down on a notepad. The final gravity reading of your homebrew should be between 1/3 and 1/4 of the OG.

Discard the sample that you took from the fermenter, as it can ruin the entire brew being fermented. Perform another test after 24 to 48 hours using the same technique. If the value of your final two results is the same, your homebrew is done fermenting.

The value of final gravity that remains stable two days in a row shows that your homebrew is ready to bottle.

Using the Manual Method

If you don’t have a hydrometer and can’t buy one either, you can still estimate whether your homebrew is fermented properly or not.

Step 1: Inspect the Yeast Inside

I recommend you use a clear vessel made of glass or plastic for the fermentation process. It’ll allow you to observe everything happening to your homebrew while being fermented. Your homebrew will start to flocculate as the yeast completes fermentation.

Flocculation is the process that produces slurry, a thick residue, at the bottom of your fermenting vessel. Your homebrew will become clearer than the liquid you had when pitching the yeast. Your homebrew will start to flocculate after the recommended fermentation time. 

Step 2: Check the Airlock

Once your brew becomes clear, the next step is to inspect the airlock. You’ll notice that your brew will start producing bubbles in the airlock when it’s fermenting. These bubbles form because of carbon dioxide produced by the conversion of sugars, indicating that the yeast is active and the fermentation process is still underway. This is the reason why you should check the expiration dates of your homebrew kits to prevent any brewing mishaps.

The number of bubbles in the vessel will lower as the fermentation progresses. The water in the airlock becomes still when the fermentation process is completed.

Step 3: Test Your Homebrew

Don’t start bottling and let your homebrew sit, even if the water in the airlock has become still. You want to make sure that your homebrew is done fermenting. Therefore, use a wine thief to remove a sample for taste and smell testing.

If it tastes or smells off, it needs more time to ferment. If it’s ready, you can move to the next step.

Step 4: Rack and Bottle Your Homebrew

Once you’ve determined that your homebrew is fermented properly, you can start bottling it. I recommend you perform the racking process before that to clarify your brew. It’s the process of transferring your brew from the primary fermenter to the secondary one to leave the cells of dead yeast and sediments behind.

Frequently Asked Questions

How Do You Know If Fermentation Has Started?

Your homebrew will start producing small bubbles on the surface when the fermentation begins. It’s the biggest indicator that informs you that the fermentation process has begun.

How Long Does Fermentation of Homebrew Take?

The fermentation of your homebrew can take five days to several weeks, depending on the ambient temperature, the concentration of sugar, and the type of yeast used. The recipe you’re using should indicate the recommended fermentation duration to follow.

Final Words

It’s critically important to make sure that you remove your homebrew from the fermenter once it’s properly ready to ensure the ideal smell and taste. I hope this guide will help you understand the right methods to know when homebrew is done fermenting to complete your homebrewing process efficiently.