ABV question.

[SkyeBrewer]

Hey folks. A friend and I recently finished a BlackBerry Stout where our recipe called for an actual secondary fermentation of the fruits.

Our OG for the primary was 1.055
The FG after primary was 1.010
Then, I added 48oz of the black berry purée when I racked to secondary.
This brought the gravity back up to 1.022

So my question is, once it’s done, assuming that it ferments down around 1.010 again, do I just add the two “fermentation’s” together to get my actual FG?

 

[ncbrewer]

Yes - add the two differences together to get ABV.
e.g. (1.055 - 1.010) + (1.022 - 1.010) = 0.057 total sg drop.

 

[Easycreeper]

To be really accurate, you'd figure out the actual starting gravity of the beer with the puree addition. I'm working off of your having 5 gallons of beer in addition to the 48 oz of puree for a total volume of 688 oz. Backing into it, it looks like the puree gravity was about 1.182, which indicates there was sugar added so it wouldn't dilute the beer.

Based on that I come up with an actual OG of about 1.064. Use this value and your finishing gravity to find ABV. However, @ncbrewer has a much simpler way of calculating that is a very good approximation.

Of course, math skills have largely abandoned me today, so I could be off... The puree gravity being so high bothers me a bit.

 

[dmtaylor]

Gravity went from 1.010 to 1.022, so you added 12 gravity points from the berries. So effectively then your OG was actually 12 points higher or 1.067. Treat this 1.067 like the real OG. So then whatever your FG ends up at, you can calculate your ABV based on that. Makes sense when you think about it.

 

[brandonlovesbeer]

Very helpfull