Find out and know when Fermentation is Complete

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Find out and know when Fermentation is Complete

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Knowing when the fermentation process can be challenging! A common question that arises in this process is: when fermentation is complete?

Understanding when your sugar wash has fully fermented is crucial for the quality of your final product.

Below are various checks to confirm when is fermentation complete. Let’s go!

Key Checks for when fermentation is complete

The fundamentals, fermentation is a process where yeast converts sugars into alcohol and carbon dioxide (CO2). Knowing when this process has ended is essential for achieving the desired alcohol content. This means it can be ready for distilling then into a bottle! How good is that?!

First, we have to know when fermentation is complete. Here are the steps to check the completion of fermentation so it’s ready for your brew. 


1. Sugar Conversion Completion

Main Indicator: Fermentation is finished when all the sugar has been converted into alcohol.

Visual Check: The top section of the fermenter starts to clear, indicating the settling down of the yeast.


2. Specific Gravity Test – Hydrometer is needed 

Initial Check: Use a hydrometer to measure the final gravity (FG). It should be in the range of 0.95 to 0.98.

Consistency Check: After the initial final gravity (FG) reading, reseal the fermenter and check again in 24 to 48 hours. If the reading remains constant, it’s a strong indication of a complete fermentation. 


3. Potential Alcohol Check

Calculation Method: Subtract the final gravity (FG) from the original gravity (OG) and multiply by a factor (usually around 131.25) to estimate the alcohol content. Formula: OG − FG × Factor = Alcohol Content


4. Airlock Activity

Observation: Before opening the fermenter, press the centre slightly. If no bubbles escape through the airlock, it suggests that is done fermenting.


5. Surface Activity

Surface Check: Once the fermenter lid is off, there should be no small bubbles or reactions on the surface of the wash.


6. Color Change

Visual Indicator: A noticeable lightening in the color at the top of the fermenter, and the beginning of separation even without adding a flocculant, is a good sign.


7. Avoid Premature Flocculation

Caution: Please do not add flocculants if fermentation is not confirmed to be complete. Premature flocculation can lead to various issues. No bueno!

Key Checks for Fermentation Completion

1. Accurate Measurement: Regularly check the specific gravity reading using a hydrometer to track the progress of fermentation.

2. Visual Indicators: Clarity at the top of the fermenter and a lack of surface bubbles are good visual cues.

3. Consistency is Key: Ensure the final gravity (FG) readings are consistent over a 24 to 48-hour period.

4. Avoid Rushing: Premature flocculation can cause more harm than good.

5. Final Alcohol Content: Use the original gravity (OG) and final gravity (FG) to calculate the potential alcohol content for an estimate of the strength of your wash.

Use scientific ways to know when fermentation is done. 

Knowing when fermentation is complete is a critical step in any brewing or fermenting process. 

By following the checks outlined above, you can do them correctly and confidently plus importantly understand why the fermentation has finished.

One thing… patience is vital in active fermentation – rushing the process can lead to unfinished fermentation or spoilage. Take notes of gravity reading during fermentation.  

Whether you’re a seasoned brewer or a newbie, these checks will guide you to know when fermentation is complete in achieving the perfect batch every time! 


Last Updated on Jan 31, 2024 by The Brew Mechanic

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With 35 years of knowledge of being a chemical engineer in alcohol manufacturing plants, my mission is to teach the next generation of home distilling alcohol brewers at a supernatural speed.

My reviews are based on real-life experiences with reflux stills, sugar wash, troubleshooting and mystical chemical reactions.

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