Question on adding bourbon to Porter

I recently brewed Northern Brewers Bourbon Barrel Porter. I ended up adding 20 oz of Makers Mark to 5 gallons of porter. Question is I know what the ABV of the Porter is but still don't know how much it is over all. Can anyone tell me how to calculate with this change. The Makers sat in a growler with oak cubes and 2 vanilla beans for three weeks before I added it to the secondary. The growler was sealed with a solid rubber stopper (not sure how much Alcohol would have been lost to evaporation if any) It sat for another 3 weeks in the porter before bottling. This was a very time consuming beer but WOW it is spectacular right when I bottled it. So worth it.

You know the volume of each and ABV of each.
5g beer x 7% ABV = .35g alcohol x 128oz/g = 45oz
20oz MM x 40% ABV = 8oz alcohol
45+8 = 53oz alcohol / (5x128 beer + 20oz = 660oz) = 8.03% ABV
Rough approximation, coverting to weight would be more accruate, but IME my measurement error is too large anyway to be that precise.

unionrdr said:

...would've been interesting to see if it can actually be measured visually.

Click to expand...

That would be interesting, though I don't think the measurement would have much meaning...i.e., you couldn't use your new OG to calculate ABV, since it changed your dilution of original wort/beer.

Think about if you added another gallon of water then took a reading - "holy smokes, my FG dropped! +2% alcohol!" Of course not, you just diluted it so your ABV drops.

The only reason the OG/FG works for alcohol is because the only density change is sugar to alcohol - if you add any other liquid without controlling for it, your measurements won't mean anything.

Just thinking out loud here.