Need some calc checks on a first time partial

Omahawk · 07-31-2009, 03:55 AM

I tried using free online software, but none of the free stuff I found lets you phase / time your extract additions. Plus, I guess I miss story problems and like doing the math myself (if a train leaves Philadelphia at 3 PM traveling eastbound at 74 mph ....).

So, reading through Palmer and trying to do the math myself (I think I understand these calculations, and how they might fit into a reasonable recipe). I'm targeting an American IPA, doing my first partial-mash and looking for a heavier single IPA. Here's my math:

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MiniMash
Mash Water 1.5 gallons for 3.5 lbs of crushed 2-row US malt and 1 lb crushed Munich.
Batch sparge 1.5 gallons.

Add water to achieve boil volume of 4 gallons. Add 2.25 lbs LME.

Gravity Calculation
3.5 lbs of US 2 row @ 70% efficiency: 28 ppg x 3.5 lbs = 98 points
1 lb of Munich @ 70% efficiency: 28 ppg x 1 lb = 28 points
2.25 lbs LME addition: 36 ppg x 2.25 gal = 81 points
Total early additions = 98 + 28 + 81 = 207 points gravity
Boil Volume = 4 gallons
SG for boil = 207 / 4 = 51.75 or 1.05175

Hops
Hop Adds =
8.6 % AA Amarillo (1 oz) at 70 minutes (utilization = 0.24)
8.0% AA Centennial (1 oz) at 40 minutes (utilization = 0.2)
5.3% AA Willamette (1 oz) at 15 minutes (utilization = 0.11)

IBU = (8.6 * 0.24 * 75 / 4) + (8.0 * 0.20 * 75 / 4) + (5.3 * 0.11 * 75 / 4) = 79.6

At 5 minutes, add 4.75 lbs LME (assume 36 ppg x 4 = 171).

OG
Add cold water after boil to achieve 5.5 gallons for fermenter. OG for fermentation = (207 + 177) / 5.5 gal = 69.8 points or 1.0698

Yeast: US 05

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Any problems with assumptions? Any problem with the disparity between the boil gravity (1.052) and the OG for fermentation (1.070)?

Thanks for the help.

**JLem** · 07-31-2009, 04:14 AM

too tired to check your math, but I stuck your recipe into BeerSmith. The OG comes out at 1.067, but the IBUs only come to 54.3. I think you need to divide by the 5.5 gallons and not just the 4 when calculating your IBUs - the way you have it will give you the IBUs of the 4 gallon boil, but not after you dilute it to 5.5 gallons.

and by "gals LME", I assume you meant "lbs LME"?

Omahawk · 07-31-2009, 11:47 AM

Quote:

Originally Posted by JLem

too tired to check your math, but I stuck your recipe into BeerSmith.

No need to do it the hard way. If I had some decent software, I would not have gone to all this work.

Quote:

Originally Posted by JLem

The OG comes out at 1.067, but the IBUs only come to 54.3. I think you need to divide by the 5.5 gallons and not just the 4 when calculating your IBUs - the way you have it will give you the IBUs of the 4 gallon boil, but not after you dilute it to 5.5 gallons.

Having different volumes and gravities at different times in the boil was the part that my free software couldn't do. My IBUs were calculated based on my boil gravity at 4 gallons. I was wondering what adding the water after the boil would do - I didn't see a reference to this anywhere.

Quote:

Originally Posted by JLem

and by "gals LME", I assume you meant "lbs LME"?

Ooops - Lbs LME is correct. Will edit now.

Thanks for the help!