Does Bottle Conditioning Add Alcohol? (Explaining the Process)

Conditioning adds the final, important touches to your brew. The process carbonates your beer and improves the flavor profile. Without it, your beer is flat. During primary fermentation, carbon dioxide escapes. To add it back, some brewers use forced carbonation, while others prefer bottle conditioning. Can this process also increase the ABV of your brew?

In bottle conditioning, the beer undergoes secondary fermentation in an airtight vessel. This process also (slightly) increases the level of alcohol. Additional yeast and sugar are added to the beer so that, when sealed, the yeast continues consuming the sugar, producing alcohol and carbon dioxide, which remains trapped within the bottle.  

Keep reading for more information on bottle conditioning, the amount of alcohol it will add to your beer, and some tips for bottle conditioning and how to measure your beer’s final ABV.

Does bottle conditioning increase ABV?

Bottle conditioning requires adding extra yeast and sugar to your homebrew. Does this secondary fermentation increase the ABV of your final beer? If so, how much?

Bottle conditioning can increase the level of alcohol in your beer, however, it’s typically not a significant change from the ABV developed by the primary fermentation.

Priming sugar is used to facilitate the secondary fermentation. Yeast consumes the sugar, creating both carbon dioxide (the carbonation in your beer) and alcohol as byproducts. This fermentation may add 0.1-0.2% ABV to the final product, the specific amount is determined by how much CO2 is created.

Although it creates a small amount of additional alcohol, this amount is generally negligible. An additional byproduct is yeast sediment, which settles at the bottom of the bottle. This sediment has a cloudy texture and a unique taste that some people enjoy. It does not affect the flavor of your beer unless left for too long.

Looking for more information on what happens if you ferment your beer for too long? Check out this article!

What is bottle conditioning?

Bottle conditioning is a necessary brewing stage to help carbonate your beer

After your beer completes primary fermentation, you still need to “gas it up.” In secondary fermentation, you add additional priming sugar and yeast, which emits carbon dioxide. That’s when the beer starts absorbing carbonation. This can somewhat change the taste of your beer, depending on the length of conditioning.

Conditioning takes time, so don’t plan to serve your beer after primary fermentation. It can take from two to four weeks, sometimes a little more. Some beers, like Belgian Ale or Imperial Stout, need longer because they have a more complex structure involving malt and yeast. 

Bottle conditioning is an important step to refining your beer.  According to the Oxford Companion to Beer, proper bottle conditioning results in a beer with “a finer, silkier texture of carbonation, superior foam retention, more complex flavors, [and] longer shelf.”

What factors affect bottle conditioning?

There are a few factors that can affect the bottle conditioning process.

Together, each of these seemingly small factors plays a large role in the conditioning process and resulting beer:

  • Style of beer – Hops-based beers, like regular or double IPAs and pale ales, are done in just a couple of weeks. However, as I mentioned just before, a beer like an English Porter needs somewhat longer. 
  • Yeast flocculation – Yeast flocculation might decrease the speed of your secondary fermentation. This means that some of your yeast becomes inactive and stops processing sugar, causing an incomplete beer. This might be a result of the yeast strain. When dealing with flocculant strains, try gently recirculating the beer to finish the process. With yeast comes sugar, which influences the results of conditioning. Priming sugar affects the color, flavor, and conditioning time. 
  • Temperature – Moderately warm temperatures increase the yeast activity, thereby hurrying along the process. The average ideal temperature rests between 68-80°F. Take note of the recommended fermentation temperature in your recipe. Too much deviation can have a negative impact on your beer. 

How does bottle conditioning increase alcohol

During bottle conditioning, the fermentation process continues inside of the bottle.

During the secondary fermentation process, carbon dioxide accumulates inside the bottle, carbonating your beer. That said, the alcohol level of your beer can increase somewhat.

Remember, fermentation creates both carbon dioxide and alcohol as byproducts. You can calculate this difference using an ABV calculator.

Does carbonation increase alcohol content?

This slight increase in alcohol is not a direct result of increased carbon dioxide.

Both the increased carbonation and the raised alcohol content are the result of continued fermentation. For instance, if you choose to force carbonate, which omits secondary fermentation, the ABV will not increase.

However, bottle conditioning causes a negligible increase, with far more positive results. 

Can you measure ABV after bottling?

There are online calculators that approximate the ABV level.  However, it can be challenging to measure your beer accurately without worrying about accidental contamination. 

According to a fellow brewer, one post-bottling measurement method is by boiling off the alcohol.

This method requires a precision scale and a water bath. Weigh out about 100 grams of completed beer, which you heat at 175°F for 20 minutes. Weigh the batch again, then return it to the water bath. Check the weight every 5 minutes. Once it stabilizes, this is the ABV.

Tips before bottle conditioning

Here are a few tips to consider before bottle conditioning:

  • Consider using at least one PET bottle. This way, you can perform a squeeze test. When the bottle is near-solid, your beer is ready. 
  • Make sure to pitch the right amount of sugar. There are calculators online to identify the right pitching weight. 
  • Condition your beer warm for much better results. I also recommend chilling the resulting beer for about 48 hours before serving.