[Steve L]

I don't know if this is a stupid question... but,
I do all grain, full volume boil, 2.5 gallon batches.
I use Martin's Bru'n water to build from RO.
I know it's set up so that the mash water additions are separate from the sparge water additions.
I do my Mash additions to match the style and profile I'm looking for, as well as correct mash PH.

Here's where I get messed up. I typically sparge with RO and I add my flavor mineral additions to the kettle.
Should I be subtracting my expected boil-off amount from the sparge water amount for fear of concentrating my kettle mineral addition by figuring it for the larger volume of sparge water?
I hope I'm making sense.
Thanks for any help.
 

[Stevie]

I do this. I never did with larger batches, but after a very mineral flavored 1 gallon batch I started doing it for all batches.

[mabrungard]

For some brewers, I've heard that they couldn't reduce their boil-off rate due to their system design. They were well above the 10 to 20 percent boil-off range. Those brewers do have to worry about excessive concentration of wort and mineral content.

For most other brewers, it is not necessary to compensate for that water loss. Just calibrate your brewing water mineral levels with your beer taste expectations and go from there. If the beer tastes too minerally to you, then back off the mineral level you target for your total brewing water volume.   

[Stevie]

Yeah, I get about a 43% evaporation on 1 gallon batches. 1.75-1 over 90 min.

[denny]

Yeah, I get about a 43% evaporation on 1 gallon batches. 1.75-1 over 90 min.

Don't measure boiloff in %.  You will not get twice as much in a 10 gal. batch as you do in a 5.  Measure boiloff in gal./hr.

[erockrph]

Yeah, I get about a 43% evaporation on 1 gallon batches. 1.75-1 over 90 min.

Don't measure boiloff in %.  You will not get twice as much in a 10 gal. batch as you do in a 5.  Measure boiloff in gal./hr.

For most calculations that makes the most sense, but when you're talking about concentrating mineral additions percentage is a good way to look at it. If your boiloff on a small batch is 25% greater than on your usual batch size, than any preboil flavor additions (such as minerals added to the mash) will likely need to be reduced by the same factor.

[Stevie]

Yeah, I get about a 43% evaporation on 1 gallon batches. 1.75-1 over 90 min.

Don't measure boiloff in %.  You will not get twice as much in a 10 gal. batch as you do in a 5.  Measure boiloff in gal./hr.

I don't normally as I use the same kettle for all 5+ gallon batches. I was just noting what I get for 1 gallon using a 3 gallon canning pot. With that pot it is about .5 per hour, my big kettle is 1.5 per hour.

[Steve L]

I've been having issues with a mineralized flavor in my IPAs which is what got me thinking about it. I do suffer about a 25% evaporation loss.


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[mabrungard]

Don't measure boiloff in %.  You will not get twice as much in a 10 gal. batch as you do in a 5.  Measure boiloff in gal./hr.

I monitor boil-off the way Denny recommends, but that has to be taken in respect to the batch size. Most homebrewing batches are probably in the 5 to 10 gal range and the typical 1 gal/hr rate applies. However, Steve's case points out that maybe we do need to also check the boil-off with respect to the total volume...that means use the % calculation also. My typical 1 gal/hr boil-off from a 6 gal starting volume suggests something in the 16 to 20 % boil-off in an hour. Someone making a smaller batch in a similar kettle might get a similar gal/hr loss, but that loss could equate to a pretty big percentage in comparison to the starting batch volume. I never thought about this before, but I think we should.

The rule of thumb can get you a broken thumb! 

[Stevie]

Martin, like I said earlier, I never thought about it until I had a nasty 1 gallon batch. Maybe I won't pay as much attention to my 5+ gallon batches.

[HoosierBrew]

I don't normally account for boil off on my mineral additions, as I lose ~ 1.1-1.2 gal/hr/5.5 gallons and like the results. But I've been considering doing smaller batches lately for certain beers and hadn't thought of the effect on mineral concentration in that case. Something to think about now.

[Steve L]

Don't measure boiloff in %.  You will not get twice as much in a 10 gal. batch as you do in a 5.  Measure boiloff in gal./hr.

I monitor boil-off the way Denny recommends, but that has to be taken in respect to the batch size. Most homebrewing batches are probably in the 5 to 10 gal range and the typical 1 gal/hr rate applies. However, Steve's case points out that maybe we do need to also check the boil-off with respect to the total volume...that means use the % calculation also. My typical 1 gal/hr boil-off from a 6 gal starting volume suggests something in the 16 to 20 % boil-off in an hour. Someone making a smaller batch in a similar kettle might get a similar gal/hr loss, but that loss could equate to a pretty big percentage in comparison to the starting batch volume. I never thought about this before, but I think we should.

The rule of thumb can get you a broken thumb!

That's the boat I'm in, I do 2.5 gallon batches, when all is said and done, for a 90 min boil I have a preboil of 4 gallons, post boil is just under 3 gallons and I get slightly over 2.5 in the fermenter.