It's a 15L fresh wort beer kit, which normally needs 8L of water addition. It is supposed to comes at 1.044 / 20 IBU with the water addition. If I don't add the 8L, brewtoad tell me it's 1.067 and 29 IBU.
Now 1.067 is perfect. But I would like to take the beer to about 40 IBU.
SInce I have spare DME on hands I could use, I would like to do a 1 litter boil of a 1.067 DME/water mix for 15 min with hops added at boil, which after being added to the 15L fresh wort would hopburst my beer to 40 IBU.
So my question is.. finally :
How much IBU this 1L addition should have to kick the beer to 40 IBU?