IBU 9l. vs IBU 19l.

Hello from Switzerland!

I'm new to homebrewing and I just start now with extract + grains.
My equipement ar a boil volum of 9 liters and my final brew are 19 liters.

When I make my recipe, per exemple a irish red ale:
-> http://www.metadelic.com/upload/irish_red.bsm

I've a IBU of 25.7 wich match perfectly the beer style.

But when I change the boil volume to compare with my next equipement (boil volum 19l.), the IBU increase to 45 IBU!!! Why?
I use for both the same amounth of hops. I'm confuse.

I'm wrong with my initial equipement? How much hop may I use to reach 26 IBU at finish?

Sorry for the newby question... but I'm lost and new at brewing. I see everywhere recipe for 5 gallons with per ex. 55gr of hop. without infos on boil volume.

Thx a lot in advance for your help.
Regards, Dom


PS: I've plan on this weeck.end a Taddy Porter clone (extract + grains)... I hope I don't will be wrong with my hop...

Welcome,

When you change the boil volume the hop utilization changes because of the concentration of the fermentables.  Increase the boil volume and the utilization rises resulting in a higher IBU with the same hop schedule.  That's just BeerSmith trying to help keep you where you want to be.

Fred Bonjour

I understand this part, but I cant understand what happen if I boil (boil volume) 9 l. with a IBU of 26 and then compense with 10 liters of cold water once the boil are over to have at finish in my fermenter 19 l. Mean that my IBU will be diluate?
If yes, that mean I can't use my equipement to brew, because I will every time have the wrong value.

How must I interpret the recipe I found on the net or into your DB?

Regards, Dom

Dom,
  A minor point, but if you enter a recipe from an external source using their settings and then use the "Scale Recipe" command to scale it to your equipment settings, you will find that BeerSmith does more than just scale the recipe up but also adjusts the color and IBU so it is the same.

Cheers!
Brad

Thx for your help. After a few tests, I've conclude that Beersmith are not suitable with my kind of equipement. I will simply forget the boil volum to calculate the IBU/EBC. I will set the boil volum on my kettle volume.

Too much confusion... If I take a recipe with per exemple a IBU of 25 for 5 Gallons. I will calculate the weight of hop on paper and I arrive to arrive at the right weight, per exemple 30g of Fuggles.

If I boil 30gr of Fuggles in 9 l. , I've the target IBU in my recipe but concentrate to match IBU 46 for 9 l., and then If I add 10 liters I've at finish a IBU of 25 for 19l.
Is that correct the way I understand?

Regards, Dominique

PS: A lot of thx for your patience.. I learn a new hobby, but whaoww what a hobby!