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General Category => General Homebrew Discussion => Topic started by: dzlater on March 28, 2010, 07:21:34 PM

Title: calculating gravity adjustments during boil
Post by: dzlater on March 28, 2010, 07:21:34 PM
I've been  reading Designing Great Beers, and it gives some formulas for hitting
your target OG by either adjusting your final volume or adding extract, or top off water.
I can follow the math in the book but was wondering if there was an on line
calculator type thing or maybe a spreadsheet to make this easier.
Or maybe a website that lays the math out in a way that's easier to use.
Anyone ever use this Beer Recipe Calculator
 http://www.northernbrewer.com/brewing/brewing-books/software/beer-recipe-calculator.html (http://www.northernbrewer.com/brewing/brewing-books/software/beer-recipe-calculator.html)
If it does what I want it to, I might buy it if I can find at one of my local shops.
Title: Re: calculating gravity adjustments during boil
Post by: a10t2 on March 29, 2010, 04:52:06 AM
No calculator required IMHO.

G1*V1 = G2*V2

When adding extract, solve for G1. To dilute, solve for V2.
Title: Re: calculating gravity adjustments during boil
Post by: dzlater on March 29, 2010, 10:45:38 AM
Thanks
I got it all figured out.
Made a couple little programs for my calculator.
Title: Re: calculating gravity adjustments during boil
Post by: dzlater on March 29, 2010, 10:48:51 AM
No calculator required IMHO.

G1*V1 = G2*V2

When adding extract, solve for G1. To dilute, solve for V2.

My problem was figuring out how much extract and how much to dilute.
Title: Re: calculating gravity adjustments during boil
Post by: a10t2 on March 30, 2010, 03:00:37 AM
If you need a hand with putting together a spreadsheet or anything, just let me know.
Title: Re: calculating gravity adjustments during boil
Post by: denny on March 30, 2010, 03:16:36 PM
No calculator required IMHO.

G1*V1 = G2*V2

When adding extract, solve for G1. To dilute, solve for V2.

My problem was figuring out how much extract and how much to dilute.

Extract is pretty easy....1 lb. of DME will add about 9 points in 5 gal.  One lb. of LME will add about 7 points to 5 gal.
Title: Re: calculating gravity adjustments during boil
Post by: dzlater on March 30, 2010, 04:18:30 PM
Thanks for all the help
I wrote three little programs for my TI85 calculator

the first program
you input, preboil gravity, preboil volume, and final volume
and gives the OG

the second program
you input, target gravity, target volume, preboil volume, and preboil gravity
and gives me lbs of DME to add, or the final volume needed to hit the OG

the third program
you input, final volume, target gravity, preboil volume
and gives the preboil gravity need to hit the OG
Title: Re: calculating gravity adjustments during boil
Post by: bbump22 on April 02, 2010, 05:47:25 PM
dzlater - would you be willing to share the actual formulas if you find time?
Title: Re: calculating gravity adjustments during boil
Post by: a10t2 on April 02, 2010, 08:00:51 PM
I know I'm not dzlater (sorry!) but they would be:

1: OG = Vpre*SGpre/Vpost

2: DME (lb) = (Vpost/43)*(Vpost*SGpost - Vpre*SGpre)
    or: Vadd = (Vpost*SGpost/SGpre) - Vpre

3: SGpre = Vpost*SGpost/Vpre

In all cases, SG is in "points" (SG - 1).
Title: Re: calculating gravity adjustments during boil
Post by: bbump22 on April 13, 2010, 10:50:24 PM
sweet, thanks!