Pre-boil volume adjustments

aubrey · 02-16-2009, 09:48 PM

Hi all. So I can't do a full boil with my new brewkettle because my stove and grill can't push it to a full rolling boil. I also can't do the recommended 2.5 gallon boil that the recipe I'm using calls for (Austin Homebrew Blue Moon clone) because my new pot is too large to do that little (its very wide) without boiling too much off, and my next largest pot is only a 8qt stokpot.

So I want to up the pre-boil volume to about 4 gallons so i can get a good rolling boil, but not boil too much off. When I did my 6 gallon test-boil, I boiled off exactly 1 gallon after an hour, with a boil that was just above a simmer (held at 210.5*F for the whole hour...)

How do I/What is the calculation to increase the boil volume? Do I just pick a number and top off to 5.25 gallons after the boil in the carboy (assuming yes on this one)? I know the amount of hops used needs to be decreased. I think the rule of thumb for going to a full boil for hops is to decrease about 15-20% but does that change if I up the boil volume but don't go full boil? I really hope this makes sense, I'll be getting started in a few hours.

Thanks in advance for the advice!

BA_from_GA · 02-16-2009, 11:44 PM

I've got the same question pretty much. I'm about to brew a AHS Belgian Wit Have a big enough pot for a full boil, but recipe kits i'm using say 2.5 gal boil, then add water when putting wort in primary.

Not to mention i hear you get better beer with a full boil, and it helps keep lighter beers from coming out darker than desired.

**Yooper** · 02-16-2009, 11:47 PM

Well, you can boil whatever volume you want. There are some adjustments to make, as you know. If you're taking a full boil recipe (converting an AG recipe for example), you'll probably need to increase the hops slightly. If you're boiling more in a partial boil, you may need to decrease the hops slightly (but probably not). The best way to figure it out is by downloading some software, such as Beersmith.

If you post the recipe, along with the original boil volume, though, one of us can run it through our software for you.

aubrey · 02-17-2009, 12:17 AM

Its the AHBS Blue Moon clone, recipe as follows (note its a 30 minute boil):

7 pounds Wheat LME
.5 pound white wheat (15 min steep at 155*)
1 pound Flaked Oats (15 min steep at 155*)
.5 pound Belgian Pils (15 min steep at 155*)
.5 pound Flaked wheat (15 min steep at 155*)
.5 oz Cascade (7.5%) 30 min
.5 oz Cascade (7.5%) 15 min
10g coriander 5 min
5g bitter orange peel 5 min
5g sweet orange peel 5 min

Recipe calls for 2.5 gal water, and then top up to 5 gal. I ran it through Beer Smith (first time I've used the software) and if I did it right, it wants me to adjust by using only .34oz of hops in each addition. Is that enough of a difference to worry about measuing it out (i have a scale around here somewhere, i just dont know where) or would it be negligable to just throw the whole .5oz in for each addition?

I've got 4 gallons on the stove almost to a boil now, so a quick reply would be appreciated.

aubrey · 02-17-2009, 02:11 AM

I just ended up saying the hell with it and added 1/2 oz for each addition per the original recipe. Cascade smells so damn good I couldn't help myself

BA_from_GA · 02-17-2009, 07:48 PM

what did you start your boil at? and what was your final quantity? ie: 6 gallon start boiled down to 5? or did you do more/less.

Thanks. I'm stoked to do my first full boil on sunday.

aubrey · 02-17-2009, 09:59 PM

Pre-boil was 4 gal and post-boil was 3.5

**Yooper** · 02-17-2009, 11:06 PM

Sorry I didn't see this earlier, but I think you did the right thing. Or, at least what I would do. .34 is close enough to .50, and you won't notice any difference. In a full boil vs a 2.5 gallon boil, you may have to make some adjustments (only in the bittering hops, though) but in a case like this, "close enough" is absolutely fine.