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 Home Brew Forums > some brew math
12-09-2010, 10:51 PM   #1
dzlater
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Location: New Jersey
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 some brew math

I wanted all my brew math in one place so I made this up today.
Figured I would share
If anyone sees something I ****ed up let me know

GRAIN BILL

ORIGINAL TARGET GU * TOTAL VOLUME = TOTAL GU

% OF FERMENTABLE * TOTAL GU = GU OF FERMENTABLE

GU OF FERMENTABLE / EXTRACT POTENTAIL / % EFFCIANCY = LBS

HOPS
The folowing is taken from Designing Great Beers by Ray Daniels
To use this you need the utilazation chart from the book
This is one of many ways to calculate hop bitterness and utilazation.

For wort with over 1.050 gravity during boil , correction factor must be applied

1+[ ( BOIL GRAVITY - 1.050 ) / 2 ] = Cgravity

IBU’s

( WEIGHT OZ. * U% * AA% * 7489 ) / (VOLUME * Cgravity ) = IBU’s

WEIGHT

( VOL * Cgravity * IBU) / ( U% * AA% * 7489 ) = WEIGHT IN OUNCES

*

CAN I MASH IT

( QUARTS PER LB * LBS GRAIN ) / 4 = GALLONS MASH WATER

GALLONS MASH WATER + (.09 * LBS GRAIN ) = VOLUME IN MASH TUN

WATER VOLUMES

PREBOL VOLUME + ( LBS GRAIN * %ABSORBTION ) = TOTAL WATER

(%ABSORBTION I USE IS 0.13 )

TOTAL WATER - [ ( QUARTS PER LB * LBS GRAIN ) / 4 ] = SPARGE
WATER

VOLUME OF GRAINS AND ABSORBED WATER AFTER DRAINING MASH TUN

LBS OF GRAIN ( .09 * ABSORB%) = VOLLUME OF WET GRAIN
I USE THIS TO DETERMINE HOW MUCH ROOM I HAVE FOR BATCH SPARGE ADDITIONS This will vary somewhat depending on kernel size, crush, etc. But it should be a decent starting point. Once you've drained your first runnings, it will over-estimate because of the soluble extract you've removed.

STRIKE WATER TEMP

[ ( 0.2 / QRTS PER LB ) * ( MASH TEMP - GRAIN TEMP ) + MASH TEMP ] = STRIKE WATER TEMP

THIS DOES NOT TAKE INTO ACCOUNT HEAT LOSS DUE TO MASH TUN THERMAL MASS

INFUSION VOLUMES FOR STEP MASH

(TARGET TEMP - MASH TEMP )*( 0.2 * LBS + MASH VOL QUARTS) / (INFUSION TEMP - TARGET TEMP) = QUARTS INFUSION = QUARTS INFUSION WATER

DECOCTION AMOUNTS FOR STEP MASH

M = GALLONS MASH WATER
L= LBS GRAIN
T= MASH TEMP
t= TARGET TEMP

{ [ M + ( 0.09 * L) ] * ( t - T ) } / ( 212 - T ) = D

D * 0.20 = E

E + D = DECOCTION AMOUNT GALLONS

GRAVITIES AND VOLUMES

THESE ARE DERIVED FROM THE EQUATION

VOL1 * OG1 = VOL2 * OG2

ADD DME TO HIT TARGET GRAVITY

OG AND MEASUERD GRAVITY ENTERED AS GRAVITY UNITS (1.045 = 45)
EXTRACT POTENTIAL FOR DME TYPICALLY 45
SUBSTITUTE OTHER FERMENTABLES BY USING APPROPRIATE EXTRACT #’S

OG = O
FINAL VOL = V
MEASURED VOLUME = v
P = POTENTIAL EXTRACT

( O * V ) - ( M * v ) / P = LBS TO ADD

BOIL OFF TO HIT TARGET OG

(PREBOIL VOL * PREBOIL GU) / TARGET GU) = FINAL VOLUME

PREBOIL VOL - FINAL VOL = BOIL OFF VOLUME

BOIL OFF RATE * BOIL OFF VOLUME = BOIL TIME
BOIL OFF RATE AS MINUTES PER GALLON

DETERMINE PREBOIL GRAVITY FROM TARGET OG

( TARGET VOLUME * TARGET GU) / PREBOIL VOL = TARGET PREBOIL GRAVITY
YOU CAN WORK THIS THE OTHER WAY TO GET YOUR POST BOIL GRAVITY

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12-10-2010, 10:49 AM   #2
Daybis
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Nice writeup of the equation. I'm gonna hve to give these a whirl this weekend.

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Ontap: Hard Cider
Primary: IIPA, All-Tythos IPA
On Deck: Munich Dunkel, Classic Rauch, Breakfast Porter, American Stout