How Much Do You Boil Off?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

golfguy819

Well-Known Member
Joined
Sep 8, 2008
Messages
189
Reaction score
1
Location
Barksdale AFB
I just finished up my 5th AG batch and was pretty shocked at how much I boiled off during this boil. I typically boil off 1.5 gallons during a 60 min boil, but today, I boiled off 2 gallons. I go into the boil w/ 7 gallons, so I can get 5.5 into the primary. But today I actually had to use tap water (I know, big NO NO, but I didn't have any bottled water around) to top off to get me over 5 gallons (I was under by a little bit).

So how much do you normally boil off?
 
Well...I burn off a gallon per half hour on my system....in the summer....more in the winter. I suspect that's what happened to you.
 
Typically one gallon per hour at a moderate boil rate. I can exceed two gallons per hour if I run the burner wide open. I've used tap water to top the fermenter up on a number of occasions without problems. When topping up, it's best to add water to the boil kettle prior to flame out which helps reduce the risk of contamination.
 
And if you boiled 15 gallons in that kettle, would you expect to boil off 3 gallons? No, it would be the same 1.5 gal.

You are right, there is no such thing as a % boil off. Because that percentage is not a constant. The rate is a constant, not a floating %.

I boil off 1.3 gallon/hr no matter the wort volume I start with, this is with about 13,000 BTUs going directly to the wort.
 
The surface area of the wort is what dictates the evaporation rate. A pot with a 12" diameter is going to boil off less that a pot with a 15" diameter at the same temp and altitude.
 
I've boiled off about 1.25 gallons per hour the four times I've used my keggle.
 
I forget to measure it and brew to Gravity as opposed to brewing to volume. I do need to put tick marks on my mash paddle though.

I think I need another one, one for my 7 gallon pot, and one for the 5 gallon. sometimes i make 2-3 gallon batches.
 
I forget to measure it and brew to Gravity as opposed to brewing to volume. I do need to put tick marks on my mash paddle though.

I think I need another one, one for my 7 gallon pot, and one for the 5 gallon. sometimes i make 2-3 gallon batches.

Or just mark one side for the 7 gallon kettle and the other side for the 5 gallon.
 
I am going to hijack here sine I got a new Kettle. I have a polarware 42qt. Any one that has one your thoughts are appreciated.
 
I'm on my 5th AG batch and I've been having trouble with the boil off. I keep collecting more and more wort but I always seem to end up shy of my anticipated 5.5 gallons. I'm always worried about the boil not being vigorous enough or pulling too much from the mash tun. I'm still experimenting and working on it. I'm bound to find a happy medium that will work. :confused:
 
it will change when there is a lot of humidty in the air like on rainy days, compared to dry hot weather.

If tap water taste good there is no reason not to use it. If it is not filtered, throw it in the microwave or on the stove top to boil off the clorine in a pinch.
 
I guess I should have mentioned that I have a 48 qt pot, so the surface area is pretty big. The tap water is fine to drink, and goes through a brita filter. I know it doesn't remove the clorine, but you cannot smell it, nor taste it. As of this morning, it's still chugging along pretty nicely.

I also know that I'm getting an accurate measurement because I drain into my bottling bucket :p Its easier to carry then a big huge pot
 
Keep in mind that the # of BTUs applied will make a large difference. I use 13,000 BTUs applied to the wort at nearly 100% efficiency.
 
how does percentage have anything to do with it?

That's just how beer smith calculates it. I boil off approx 1.5gallons in an hour with a 5.5 gallon batch. Therefore i'm boiling off around 22%.

If that's how they figure it, that's good enough for me, my numbers are usually spot on.
 
That's just how beer smith calculates it. I boil off approx 1.5gallons in an hour with a 5.5 gallon batch. Therefore i'm boiling off around 22%.

If that's how they figure it, that's good enough for me, my numbers are usually spot on.

Yeah, the beer smith developer was lazy. Percentage works, but ONLY for your system and batch size. If you alter your batch size, 22% is invalid. It's a useless number for comparing with other brewers.
 
Yeah, the beer smith developer was lazy. Percentage works, but ONLY for your system and batch size. If you alter your batch size, 22% is invalid. It's a useless number for comparing with other brewers.

Thats odd it boils the same for a double batch as it does a single.
And the question was how much do you boil off, so how is that useless to the op?
 
Yeah, the beer smith developer was lazy. Percentage works, but ONLY for your system and batch size. If you alter your batch size, 22% is invalid. It's a useless number for comparing with other brewers.

Actually, Beersmith (who's a member here) didn't make this decision unilaterally. For whatever reason, the BeerXML specification specifies the units for boiloff rate to be in percent per hour.

I've asked about a change in upcoming versions of Beersmith so we can specify boiloff in volume per hour.
 
The same amount, which would then be 11% and not 22%.

Right, if I do a 10 gallon batch, I boil off 1.3 gal/hr (13%)

If I do a 5 gallon batch, I boil off 1.3 gal/hr (26%)

Same volume, different %
 
I typically boil to gravity as well, depending on my gravity at the end of the mash and sparge.

If I am under my target gravity I will get a rolling boil for the entire hour. If I am at my target gravity and near my target volume, I have a slow & steady boil and put my lid 3/4 on to prevent the majority of evaporation while allowing for no boil over.
I use a 60,000 btu camp chef burner which you can adjust your propane flow pretty easily. If you are boiling on an electric stove, the limitation is high is pretty much the best boil you can get...

Depending on how much evaporation (by wind or aeration from the boil) you can adjust boil off amount from 1/2 gal to 2 gallons per hour. The key is taking good notes.
 
Back
Top