When adding fruit or juice to mix after pimary fermentation, what is the prosses to adjust sg calc for an accurate end result
It would be easiest to do a weighted average. This takes in to account the added volume of your juice and requires no assumptions of when you're batch will go full dry.
So take you initial Sg, your Sg going into secondary and determine your current alcohol. Write this number down and call it 1
. Subtract your current alcohol from your original potential alcohol, and you have your current theoretical potential. Call this A
Prepare your addition at secondary and take a Sg reading to determine the potential alcohol of your addition. Call this B
Now multiply A
by the size of your original batch in ounces C
, and multiply B
by the size of your secondary addition in ounces D
Add AC to BD, and divide by C+D. Call this E
is your new potential alcohol moving forward in secondary.
At the end, take a Sg reading and determine your final alcohol potential. Call this F
equals your alcohol production in secondary. Call this 2
final alcohol is 1+2
(edit)NOTE: this will be as accurate as you can get for a juice addition. for a fruit addition, crush and cold-soak the fruit to get the most accurate sugar reading possible, then treat it like a juice addition. most fruit are more water than solids, so the fruit itself won't skew your numbers too much.