I was wondering how you'd break down Mitch Steele's hopping schedule for his recipes in his IPA book. For example, for one beer he writes "Total boil time is 90 minutes. Using only pellets, add 62.5% Columbus at the start of the boil, then add 37.5% Centennial during the whirlpool." How do you determine how much at what IBU? Thanks to anyone who can help. This is for a 105 IBU beer.

Perhaps someone that has a copy will be able to chime in. I haven't read it yet, so don't want to put words in Mitch's mouth... but when you say IBU, do you mean AA%?

At the beginning of the recipe section it says regarding hopping: "Percentages are based on the total weight. Remember, however, that this number is a starting point--thus, you will have to calculate the utilization for your equipment"

Some of the recipes look like they have aa% for each hop, others don't. It looks like you are looking at the Ruination recipe. I'd use a calculator and just start plugging numbers in at whatever AA% your hops are until the numbers come out right. I've never seen a calculator that knows about whirlpool hop bitterness, so I always put those as 1 minute hops figuring they will get some bitterness in but you also lose a lot of bitterness as the yeast drops out so it probably averages out. If someone has better data, I'd love to see it.

For 105 total ibu's, you would need 65.63 IBU's from your columbus addition and 39.38 IBU's from your centennial addition, for whirlpool, calculating it as a 15 or 20 minute addition, a la Jamil. Beersmith would make this really easy. However, I haven't read the book yet, so I could be talking out of my @$$. Happy Yom Kippur.

He brew?

I derived an equation that allows you to calculate the total weight of hops, in ounces, using the Rager formula:

wtot = (Total IBU*Vfinal*Cgravity)/(sum(%wi*%AAi*%Ui*7489))

wtot = total weight of hops, in ounces

Numerator
Total IBU = Number quoted in Mitch Steele's Analytical targets section for each recipe
Vfinal = final volume of boil, in gallons
Cgravity = gravity correction factor as defined by Ray Daniels book, Designing Great Beers = 1+[(Gboil-1.050)/0.2]

Denominator
"sum" indicates you need to add the IBU contributions from all of the hop charges in Steele's recipes
%wi = decimal form of the weight percentage of the ith hop charge as quoted by Steele
%AAi = decimal form of the percent alpha acid of the ith hop charge
%Ui = decimal form of the percent utilization of the ith hop charge based on times quoted by Steele

Once you solve for wtot, you can back out the individual weight of each charge by using Steele's weight percentages.

e.g. Pliny clone; Total IBU = 92, Vfinal = 6.16 (15% evap rate from 7.25 gal preboil volume), Cgravity = 1.05

40% CTZ, 90 min, 14.00%AA, 22.6%U,
9% Simcoe, 45 min, 13.00%AA, 19.4%U
11% Centennial, 30 min, 10.00%AA, 16.2%U
40% blend, KO, 0%U (assumption)

From the above formula, I calculate a total weight of hops of 4.76 ounces. I backed out the following weights for each charge:

1.90 oz. CTZ
0.43 oz. Simcoe
0.52 oz. Centennial
1.90 oz. blend

Confusing? Perhaps. Thoughts?

I don't have the book, but when I see recipes stated for percentages of IBUs, I use the AA% of the hops on hand to determine the IBUs at the time. 62.5% of the 105 IBUs is coming from the bittering hop addition. So in BS, put the AA% of the hops you have as a 90 minute addition and adjust the weight until you get the 62.5% of the 105 IBU that you need, which is 65.625 IBU. Use the amount of hops in your volume to get that IBU for bittering addition. You'd leave 39.375 IBU in the whirlpool to make your complete 105 IBU for the beer.

I recall in a recent (2012) show where Tasty and Doc were discussing a mini topic about extracting bitterness from the whirlpool and how to calculate it. IIRC, Tasty said to enter it as a 20 minute hop addition to factor the IBUs, but put them it at the whirlpool instead of 20 mins. You're just using the 20 min set point for IBU calculation.

To add...........The rationale for inputting whirlpool hops at 20 minutes is that during the whirlpool, the wort is still at boiling temperatures, or close to it. Therefore, isomerazation is still taking place. Therefore, you need to also take into account the amount of time the hops are in the whirlpool, whether 10 or 20 min and use that as your reference. I could see the argument for moving the hops to 20 minutes instead of steeping them after the boil.