Impact of priming sugar on ABV

[Brewer #108287]

How can I determine the final ABV following bottling? Is there a formula to do so? I've been calculating ABV by taking OG prior to pitching yeast and then FG following fermentation in fermenter and hadn't realised that there could be a significant impact on ABV from priming in the bottle. For example, OG of 1.047, FG in fermenter of 1.013 and then 1.008 after a few weeks in bottle. For this ale it means a true ABV of 5.1% and not 4.5%. Any help and advice greatly appreciated!

 

[The Brew Mentor]

It's insignificant.
Sound to me like you bottled too early or had an inaccurate FG reading.
Were they over-carbonated?

 

[jeffpn]

Most people don’t worry about it. If you want to find out, I suppose you’d have to add the sugar like it was in your recipe, assume the OG to be higher by 2 or whatever points than it really was when measured pre-pitch, and then measure the gravity of a bottle after it’s conditioned.

 

[BOB357]

For normal carbonation levels if you figure 2 or 3 points added you'll be just as close as anyone not brewing commercially needs to be.
You'll likely be within the same margin of error that you get using OG, FG and a calculator. Hey, it's beer. Drink it and be happy!

 

[Nosybear]

You're adding 2 points of gravity. That adds about 0.25% ABV. 0.39% if adding 3 points. Worth adding? Your call.

 

[Brewer #108287]

Guys, many thanks for your replies - much appreciated. Reason i'm needing to be accurate is that i'm planning to start selling commercially on a very small scale at local markets etc later this summer. Looks like the concensus is that i'm addding about 2-3 gravity points. May be a daft question, but can i condition in bottle and not add any priming sugar. I thought i had to to ensure good carbonation etc?

 

[BOB357]

If you're going to sell any alcoholic beverage you'll need licensing from one or more agencies. They will lay out the rules and likely specify the means by which you reach the numbers required in labeling.

 

[jeffpn]

Guys, many thanks for your replies - much appreciated. Reason i'm needing to be accurate is that i'm planning to start selling commercially on a very small scale at local markets etc later this summer.

Yeah, no you’re not! Selling homebrew is illegal in the States, if that’s where you live.

 

[Hogarthe]

If you bottle before reaching final gravity you can let it finish in the bottle so it carbs. But you have to watch the gravity close to know when to bottle and you have to be consistent in your brewing so you know what final gravity will be. If you think it will reach 1.010 and bottle at 1.012, but it stays at 1.012, you will have flat beer. If you bottle at 1.012 and it goes to 1.008 you will have overcarbed beer.

 

[Nosybear]

Guys, many thanks for your replies - much appreciated. Reason i'm needing to be accurate is that i'm planning to start selling commercially on a very small scale at local markets etc later this summer. Looks like the concensus is that i'm addding about 2-3 gravity points. May be a daft question, but can i condition in bottle and not add any priming sugar. I thought i had to to ensure good carbonation etc?

Commercially, you would need to add in the alcohol produced by bottle carbonation. Just add either 0.25% or 0.4%, depending on the amount of sugar in gravity points you're adding. There is a way to condition without adding sugar, it goes like this: When you brew, do a forced fermentation test on each batch - take a sample of pitched beer (make sure you stir to distribute the yeast evenly), ferment that sample at elevated temperatures and when it's done, take a gravity reading. That will tell you what your minimum final gravity will be. When you're two or three points above that, bottle without sugar added. It solves the problem of adding sugar and increasing your ABV, it just isn't as accurate at predicting the CO2 levels. And if you're going commercial, consistency is your first priority.

 

[Nosybear]

If you bottle before reaching final gravity you can let it finish in the bottle so it carbs. But you have to watch the gravity close to know when to bottle and you have to be consistent in your brewing so you know what final gravity will be. If you think it will reach 1.010 and bottle at 1.012, but it stays at 1.012, you will have flat beer. If you bottle at 1.012 and it goes to 1.008 you will have overcarbed beer.

Or bottle bombs - you don't want a customer having a bottle bomb even more than you don't want one for yourself. That's an aspect I didn't discuss above - safety.

 

[Hawkbox]

If it's legal where you are good luck, I have been told by a few people I should try and go commercial and I just ask them why I would want to take such a huge pay cut.