Adding Extract to reach desired gravity when PM or AG brewing

[jmkratt]

I did a search but didn't see anything but I am not confident with the terms I used.

Anyhow, I am brewing Partial Mash batches. At times My gravity readings for both boil and upon pitching are low. I have been using my refactometer for the readings. I know that I have read where some people brewing PM or AG will keep some extract on hand to throw in the boil in the event they are short in the gravity readings.

My question: Is there a quick way to calculate how much extract is needed on the fly? I know I can add it in Beersmith, but when I am brewing I don't have access to the software. I am assuming people aren't just blindly adding extract but perhaps I am off-base.

Any input would be extremely appreciated!

Thank you

 

[Seven]

This post may help you. I'm curious to know if anyone has a more simpler method than what is described in that post.

 

[wonderbread23]

If you're using dry extract to make up the points:

Example:
-You're make 5 gallons of 1.060.
-Your preboil gravity is supposed to be 6 gallons at 1.050.
-Your actual preboil gravity is 6 gallons at 1.042

The final beer has 300 gravity units in it (5 gallons X 60 GU). Your preboil wort has 252 gravity units in it (6 gallons X 42 GU). This means you're short 48 gravity units.

Dry extract is 45 GU/Lb/Gallon. 48 / 45 = 1.06. This means you need to add 1.06 pounds of dry extract to hit your target final gravity.

 

[jmkratt]

If you're using dry extract to make up the points:

Example:
-You're make 5 gallons of 1.060.
-Your preboil gravity is supposed to be 6 gallons at 1.050.
-Your actual preboil gravity is 6 gallons at 1.042

The final beer has 300 gravity units in it (5 gallons X 60 GU). Your preboil wort has 252 gravity units in it (6 gallons X 42 GU). This means you're short 48 gravity units.

Dry extract is 45 GU/Lb/Gallon. 48 / 45 = 1.06. This means you need to add 1.06 pounds of dry extract to hit your target final gravity.

That's perfect.

Thank you for the help guys :rockin: