Brak23

Recipes 

Hey everyone,

Just got iBrewMaster and I feel like the IBU calculation is a bit high. On my porter with a 5 gal boil its saying something like 80 IBU for it. If I cut it to a 3 gal boil it goes to 40. Just seems like all the recipes have a higher IBU listing versus other apps and software. Or is it just me?

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Remington Brewery
Homebrewing since 2011

Grinder12000

Recipes 

I'm not a fan of iBrewmaster as it does not do a LOT of what I want - it's more of a recipe all I feel!

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Grinders Island Brewery - Pipeline (Batch #)

Primary #1 Hair of the Arm West Coast Blaster - don't ask(89)
Next up - Award winning Dbl Chocolate Stout Batch #4 (90) On deck - Zythos Pale Ale(91) and then Weizenbock(92)

MikeMetroka

Recipes 

Brak23
What hop are you using and what is the AA. What quantity?

Brak23

Recipes 

Its 1.75 oz of Summit Hops (18.20%) for a full 60 minute boil. That creates 81.93 IBU

If I do a 3 gal boil, its only 43.30 IBU. Just seems really high.

The recipe I'm using is an Extract Kit from NorthernBrewer.com, its an Imperial Stout.

But why does the half boil or full boil make such a large difference in hop utilization?

MikeMetroka

Recipes 

From what I understand, the 3 gal boil would be a much higher gravity and would have a lower percentage yield or the hops.
The larger 5 gal boil with lower gravity would yield higher utilization.
Have. You plugged this recipe into other software?
MM

Brak23

Recipes 

But wouldn't the 3gal boil with 2gal of additional water at the end = a full 5gal boil with no added water in the end? I just always assumed that.

Also, I plugged in the hops into a different program and got ~83 IBU again. So the program is right, just wondering why the imperial stout has a higher IBU.

MikeMetroka

Recipes 

I don't want to sound like I'm repeating but the specific gravity of the wort has great impact with hop utilization.
"the higher the specific gravity of your boiled wort the less efficient the extraction of bitterness will be."
Charlie Papazian, The new complete joy of homebrewing page 266.

TipsyDragon

Recipes 

Which IBU calculation are you using in the app? iBrewMaster lets you chose between several formulas. Also if you decrease the boil size the app assumes ALL the fermentables are in the boil, hence the higher preboil gravity listing. Higher preboil gravity should and does lower the IBU calculation. The post boil (topped off) gravity of the brew has no barring on the IBU calculation at all.