Partial Boils

[rodwha]

I had read that there was little difference between the IBU's of a partial boil and a full boil, though I'm not sure how much top off there was. When calculating my latest IPA I was instructed that by using 2 gals of top off in a 6 gal batch in effect cut my IBU's by 1/3.

This has lead me to wonder how I could get closer to a full boil with what I have as my new house has a glass top and I've read I can likely expect a weaker boil which has now redirected me from increasing my brew pot size for now.

Could I boil 4 gals in my 5 gal pot and use my partial mash wort for the bittering, and then use my extract in the ~6 qt pot for my flavor/aroma additions to cut out the bulk of my top off? Does it work this easily or is it not quite so straight forward?

And how does it work out if I use only LME for top off vs water? Does that change anything?

 

[Calder]

Boil about a third of the extract in 3.5 to 4 gallons, and hop normally, then add the rest of the extract at flameout. This will improve hop utilization, result in a lighter beer, and the late extract will help with cooling.

Doing it this way, you will not notice any difference to this and a full boil.

 

[rodwha]

I've been using about 1/2 grains in a mash in a 4 gal boil and adding the extract at the end in addition to ~2 gals of chilled water for top off, but I was told that by having 1/3 of my final volume as top off that it reduces my IBU's by 1/3. It's not such a big deal with typical beers, but it becomes a problem with hop bombs.

My latest IPA (105 IBU's on paper) would likely only be in the high 60's, but it tastes as though it's in the low 40's despite using a very tiny bittering addition and loading up on the flavor/aroma/dry hops. And that's why I'm considering a new game plan.

All of my previous IPA's have tasted about what the numbers have claimed, but I've used a larger bittering addition and had my IBU's between 65-75.