Hop utilisation, beer smith and ibu/ebu's

[badgerdan]

I have a recipe in Beer Smith but am getting confused about the rules on hop utilisation. My brew states 35 IBU's but that's if I boil 2.5kg dme in the full 20 litres of water. I want to be boiling about 10 litres with half the DME as I heard this is then better for the utilisation but in Beer Smith when I add the info 20 litres total and 10 litres boil it then gives me an IBU of 35 too, has this then accounted for the fact that I'll be adding 10 litres of water and then 'watering' down what's currently been extracted? Would the IBU after the boil in 10 litres actually be much higher but BS only shows what it will be when the rest of the water is added?

Also what are the differences between IBU's and EBU's and which formula for bitterness should I use; Tinseth, Rager or Garetz. Each one gives me a huge difference in IBU number.

For example:
Tinseth gives me an IBU of 35.2
Rager gives me an IBU of 42.2
Garetz gives me an IBU of 25.6

Depending on which one I use could have a huge bitterness difference :/

[soupdragon]

I have a recipe in Beer Smith but am getting confused about the rules on hop utilisation. My brew states 35 IBU's but that's if I boil 2.5kg dme in the full 20 litres of water. I want to be boiling about 10 litres with half the DME as I heard this is then better for the utilisation but in Beer Smith when I add the info 20 litres total and 10 litres boil it then gives me an IBU of 35 too, has this then accounted for the fact that I'll be adding 10 litres of water and then 'watering' down what's currently been extracted? Would the IBU after the boil in 10 litres actually be much higher but BS only shows what it will be when the rest of the water is added?

Also what are the differences between IBU's and EBU's and which formula for bitterness should I use; Tinseth, Rager or Garetz. Each one gives me a huge difference in IBU number.

For example:
Tinseth gives me an IBU of 35.2
Rager gives me an IBU of 42.2
Garetz gives me an IBU of 25.6

Depending on which one I use could have a huge bitterness difference :/

Hi badgerdan

Simple answer is yes....... As long as you maintain the same ratio of fermentables/liquor then your utilisation will be as near as makes no difference the same but because you're using the full quota of hops rather than a reduced amount the wort will have a higher IBU. And as you said, once you've diluted to your full brew length you'll end up with you desired bitterness.
As regard your other question about IBU/EBU, I really have no idea but I'm sure the more knowledgeable members will be along soon enough

Cheers Tom

[oz11]

I think IBU and EBU is much the same thing...this forum post seems to suggest the same http://www.homebrewtalk.com/f14/ebu-vs-ibu-32161/