No boil extract for Strong Scottish Ale

[CButterworth]

I am trying my hand at an extract based Strong Scotch Ale. I got some feedback in a previous thread, but then realized that I cannot do a large enough boil volume.

Somewhere, I read about adding the extract post-boil (or late boil). However, I get weird bitterness values in Beersmith 2 if I drop the amount of extract too low.

I'd appreciate any thoughts or opinions.

7 lbs Amber Liquid Extract (12.5 SRM) - POST BOIL
6 lbs Amber Liquid Extract (12.5 SRM) - boil 60 minutes
11.0 oz Caramel/Crystal Malt - 60L (60.0 SRM)
6 oz Aromatic Malt (26.0 SRM)
6 oz Smoked Malt (9.0 SRM)
2.2 oz Roasted Barley (300.0 SRM)
1.6 oz Fuggles [4.50 %] - Boil 60.0 min
1.6 oz Goldings, East Kent [5.00 %] - Boil 60.0
1 pkg Edinburgh Ale (White Labs #WLP028) - made into a starter

In Beersmith2, this gives the following stats:

Est OG: 1.086
Bitterness 27 IBU's
Est pre-boil gravity: 1.122

When I move more of the extract into the post-boil, the number of IBU's jumps dramatically to over 60 IBU's. Is this due to hop isomerization? Would it really be that high? Or maybe Beersmith2 has a quirk? Or operator error????

Somewhere else, I read about adding all the extract after the boil and reduce hop usage by about 20%????

Any ideas?

Thanks,
Charlie

 

[Epimetheus]

Here is a good description of the effects of adding extract late in the boil or even after the boil. See answer #1, that describes it in one short paragraph:

The point behind adding the LME late in the boil or straight to the fermenter is that the sugars in the LME will undergo the Maillard reaction during the boil. The gravity also affects the hop utilization rate. You need SOME sugars in the wort to isomerize the hop alpha acids, but the stronger the wort the less a given hop addition will bitter.

I am new at brewing; your question made me wonder about it and do some research. Thanks!

 

[CButterworth]

Yeah, that's pretty much what I read in one of my beer books. Of course, I want to be sure that my numbers are within the ballpark for bitterness as I'd hate to get the beer into the keg then find out that the bitterness was strong enough to remove bring tears to the eyes of the taster and all those in close vicinity!!!!!

Charlie

 

[Yooper]

That's a quirk- you won't get 60 IBUs with only 3 oz of low AAU hops. The reason is because the calculator takes wort gravity into account, but it's recently been found that IBUs are not really dependent on wort gravity.

Are you doing a partial boil or full boil? If you're adding water at the end of the boil, you'll also be "diluting" the IBUs then as well.