Understanding Carbonation and ABV

[Hopperty]

Did a brew about 6 weeks ago, starting at 1048, I bottled it a fortnight later at 1016 adding a ½tsp sugar (which I guess would have taken it back up to 1018.

Just done a reading tonight and it is now at 1013

Would I calculate the final fall in gravity towards alcohol content ?

so effectively it has fallen by 0.037 which would give 4.85 abv
or would I just use the original fall of 0.032 (4.2 abv)


It is a bit lively in the bottle, just taking the top off had it frothing out of the bottle - but once I got the gas out of it, what a lovely drop of beer (Munton's Porter)

 

[Clint]

It may not have been done at 1016..some can take up to a month to hit fg.

 

[Hopperty]

I know it seems a bit obvious, but i'm not a 100% sure on this.
The carbonation and small fall in gravity within the bottle - does this add to the alcohol content ? or has the yeast finnished and the alcohol level will remain as it was before bottling ?

 

[DavidDetroit]

Yes, it would be calculated toward ABV. The changes in gravity readings indicate an increase in alcohol, basically. If you want, add the 1/2 t, take a gravity reading and then another when the "FG" of the bottling sugar is reached and then add to the pre-bottling OG/FG reading . Basically you would be taking two sets of readings. Of course, very few, if any, people do this as a regular practice since the ABV achieved by bottling sugar is minimal. I've seen it pegged at 1/2% increase.

From the liveliness, it sounds like the beer wasn't done fermenting in the FV. A 1.016 gravity is high, generally, for a low ABV beer. Fermentation temperature is good to know in a situation like this and is important for various reasons. The beer should be complete after two weeks but without knowing your fermentation temp, who's to say? And, as pointed out earlier, it can take longer.
In the future, take two gravity readings a day or two apart to ensure fermentation is complete.
You could/should keep them in the fridge so they don't condition further. Or recap them all. It's not an ideal situation you have there. I'd be careful with handling them and use safety glasses at the minimum.
Good luck.

 

[parpot]

I bottled a brew a bit too early a few months ago but thankfully I put it into PET's so managed to burp the bottles a few times before drinking and it ended up as a fantastic beer!

 

[terrym]

I know it seems a bit obvious, but i'm not a 100% sure on this.
The carbonation and small fall in gravity within the bottle - does this add to the alcohol content ? or has the yeast finnished and the alcohol level will remain as it was before bottling ?

Yeast works on fermentable sugars to produce alcohol and CO2. In the primary it's all about alcohol production, and CO2 is a by-product (at least for homebrewers). Priming is all about CO2 production but alcohol is still produced, and so the ABV will increase by a small amount.

 

[Nicks90]

"I bottled it a fortnight later at 1016 adding a ½tsp sugar (which I guess would have taken it back up to 1018.

Just done a reading tonight and it is now at 1013"

how did you do a gravity reading on carbonated beer? the hydrometer will be covered in bubbles which will totally make it inaccurate.

 

[terrym]

how did you do a gravity reading on carbonated beer?

Spin it to dislodge the bubbles.

 

[DavidDetroit]

I bottled a brew a bit too early a few months ago but thankfully I put it into PET's so managed to burp the bottles a few times before drinking and it ended up as a fantastic beer!

That's a good fix for the situation. I have to say, safety-wise, you can't beat a PET bottle and they are quite forgiving. Worst case scenario would be just beer sprayed in the general vicinity which is far preferable to glass shards.
It wouldn't be the worst idea for all new bottlers to start with (or stay with) PET bottles. For me, I was instilled with a deep terror of bottle bombs right from the get go and so took far too many FG readings in the beginning.

 

[DavidDetroit]

Spin it to dislodge the bubbles.

I always take my OG reading from the FV and I tried spinning my hydrometer a few different times at around 3,000 RPMs (slight exaggeration) and still couldn't get the bubbles to shed. I have to gently "dig" a hole in the foam and then place the hydrometer. Do you have to do it a few times in a row or what?

 

[Hopperty]

"I bottled it a fortnight later at 1016 adding a ½tsp sugar (which I guess would have taken it back up to 1018.

Just done a reading tonight and it is now at 1013"

how did you do a gravity reading on carbonated beer? the hydrometer will be covered in bubbles which will totally make it inaccurate.

degas it first by shaking all the bubbles out of what I'm going to test (until it's completely flat) then do a reading - then drink it

 

[dad_of_jon]

Did a brew about 6 weeks ago, starting at 1048, I bottled it a fortnight later at 1016 adding a ½tsp sugar (which I guess would have taken it back up to 1018.

Just done a reading tonight and it is now at 1013

Would I calculate the final fall in gravity towards alcohol content ?

so effectively it has fallen by 0.037 which would give 4.85 abv
or would I just use the original fall of 0.032 (4.2 abv)


It is a bit lively in the bottle, just taking the top off had it frothing out of the bottle - but once I got the gas out of it, what a lovely drop of beer (Munton's Porter)

take 1048-1016 to start with then measure primed beer say 1018 then defizz a bottle and measure that say 1014 so thats a drop of 32 + 4 points which you can bung into a calc for the answer. A lot of us add .2% abv on cos measuring the second set of readings is more faffier