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 Home Brew Forums > Looking for Formulas: IBU, Extract amount from grain, etc.

11-06-2006, 04:42 PM   #1
ian

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Jul 2005
Pendleton, SC USA
Posts: 473
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Anybody got some good sources. I have software but am wondering how all of this is calculated. I've seen some forumlas but nothing very in depth.

So, anybody got any? Just curious how you guys designed your personal spreadsheet based recipe calculators

Thanks!
Ian

11-06-2006, 04:55 PM   #2
david_42

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Oct 2005
Oak Grove, Oregon, USA
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Well, there really aren't many formulas. The bulk of the calculations are extrapolations between imperially derived data points. A good example is bittering for hop additions under five minutes is ignored. "The Charts" start at 5 minutes, but utilization at 5 minutes is already 1/5 that of a 60 minute boil.
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11-06-2006, 05:01 PM   #3
Evan!

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Aug 2006
Charlottesville, VA
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David,

5 goes into 60 12 times---how do you get 1/5th? Is it not a consistent variable?
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11-06-2006, 06:08 PM   #4
ian

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Jul 2005
Pendleton, SC USA
Posts: 473
Liked 5 Times on 5 Posts

OK, so no one has an actual formula?

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11-06-2006, 06:14 PM   #5
ian

Recipes

Jul 2005
Pendleton, SC USA
Posts: 473
Liked 5 Times on 5 Posts

I found this page which has two IBU formulas.

Does anyone have any idea if one is better than the other? Or if these are ones currently used by any of you?

11-06-2006, 06:21 PM   #6
magno

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Feb 2006
Austin, TX
Posts: 900
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Check out the book "Designing Great Beer". It is full of formulas.

- magno

11-06-2006, 06:53 PM   #7
uwmgdman

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Feb 2006
Oregon, WI
Posts: 687
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Quote:
 Originally Posted by magno Check out the book "Designing Great Beer". It is full of formulas. - magno
Ditto that........I made my brewing spreadsheet from most of the equations in that book. I use Palmer's equation derived from fitting data points for IBUs and adjusted it a little bit to what I thought echoed my setup.

11-06-2006, 07:45 PM   #8
ian

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Jul 2005
Pendleton, SC USA
Posts: 473
Liked 5 Times on 5 Posts

Umm, how's about typing them in??

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11-06-2006, 09:43 PM   #9
magno

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Feb 2006
Austin, TX
Posts: 900
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If they're not up when I get home I can put them up. The IBU calculation is pretty straight forward, but the amount of extract from grain has a table with several types of grain listed. Anything else that you are after?

- magno

11-07-2006, 01:03 AM   #10
magno

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Feb 2006
Austin, TX
Posts: 900
Liked 9 Times on 6 Posts

OK, here goes:

To calculate the amount of various grains needed in a recipe, multiply the wort volume by the anticipated OG (OG in gravity units, ie. 1.044 = 44 GU).

5.5 gal * 44 = 242 GU

Multiply this product by the percentages of the various grains that you want to use. In this example they use 60% two row, and 20% each wheat and honey.

2- Row: 242 * .60 = 145 GU
Wheat: 242 * .20 = 48.4 GU
Honey: 242 * .20 = 48.4 GU

To calculate the amount needed of each grain, take this product and divide by the extract potential given in the table and then divided by the mash efficiency. In this example they assumed a 68% mash efficiency, except for the honey, which gets 100%.

2- Row: 145 / 36 / 0.68 = 5.92 lbs
Wheat: 48.4 / 38 / 0.68 = 1.87 lbs
Honey: 48.4 / 33 / 1.00 = 1.46 lbs

The extract potential table is about like this:

Ingredient:...........................Extract Potential (GU)
Chocolate, black, roast ...............25 - 30
Crystal, Cara...............................33 - 35 (darker = lower)
Munich, Vienna, mild, Biscuit.........35 - 36
Pale, Pilsener...............................35 - 37
corn.............................................. 37 - 39
oats.............................................. ...33
rye malt............................................29
malted wheat...............................37 - 40
wheat, rye (unmalted, raw, flaked)..36
cane sugar.......................................46 From here and below use 100% mash efficiency.
corn sugar........................................37
DME............................................... ..45
honey..........................................30 - 35
LME..............................................3 7 - 39
maple syrup....................................30
molasses.........................................3 6

The IBU equation is a bit more involved:

IBU = Woz * U% * A% * 7489 / Vgal / Cgrav

where Woz is the weight of the hops in ounces, U% is the utilization as a decimal, A% is the alpha acids as a decimal, V gal is the volume of wort when you pitch the hops, and Cgrav is the correction for gravities over 1.050

Cgrav = 1 + [(Gboil - 1.050) / 0.2]

where Gboil is the SG of the boiling wort.

The utlilization is found using this table:
Boil Time (min)...........whole(%)................pellet(%)
dry hop..........................0.................... ..........0
0 - 9...............................5................. .............6
10 - 19..........................12.................... ........15
20 - 29..........................15.................... ........19
30 - 44..........................19.................... ........24
45 - 59..........................22.................... ........27
60 - 74..........................24.................... ........30
75 +..............................27................. ...........34

All said, I cannot recomend this book enough (Designing Great Beers by Ray Daniels). After Charlie P. gets you into the basics this is the next logical step. The first part of the book goes over basic recipe formulation, and minimal brewing technique, the second half is all about different styles of beer in detail. Great book.

Hope this is what you are after.

- magno

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