About adding hops to the boiling wort

[migi]

Hi guys,
Last week I did my first partial mash biab, basically what I did: 1)Normal-mash biab in 11L (19L-pot, ~3Kg of grain) 2)add part of the LME before start to boil 3)Boild&add the hops and 4)Add more LME and water until reach 21L or my target OG (1.062).
I made the mistake of expect a 75 efficiency and finally it was 53. So I am afraid the bitterness is going to be really high (the target was 42, but now is ~55).

I have been using the brewersfriend calc recipe and I understand that doing `late additions` of LME, it increases the final IBU, because the wort is less dense. So what happened, I guess, is because my efficiency was so low, the `extraction` of bitterness was too high. Actually once in the fermenter, I saw a layer of clear wort in the surface. It is normal? It looked like oily.

What is the difference if I use less extract before boil the wort and mix all together once the boil is finished? In that case I would use less hops. In the most extreme case, why can't boil the hops with water and once it finishes, add to my wort? I guess the hop have to be boiled in wort because if not the bitterness is different or something?

Cheers,

 

[mongey]

I only did a few partials before moving to all grain but I never boiled the Can .I mashed, drained then did the hop boil . then added to the goo in the fermenter and then topped up to where i wanted it ,volume and OG wise , with tap water .Just seemed easier to work out what was going on

but I was never too jazzed on what the actual IBUs were. I had a good of idea of what was too much from doing full tin recipes and went with the flow