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..............................................37 - 39
maple syrup....................................30
molasses.........................................36
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
