What is your Boil Off?

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calvey

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I am trying to come up with some meaningful defaults for http://biabcalculator.com. In looking at the Boil Off value I hear some wildly different values. I lose around 1.25 gallons per hour with keg and propane turkey burner.

How much do you boil off per hour and on what kind of setup?
 
I brewed last week and lost 1.25 gal per hour. It was 72 degrees and about 75% humidity. I had a rolling boil but would not say it was too vigorous. Single tier brew stand with keggle. The burner looks like a BG 14 with an inner ring.

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I just bought a new kettle three days ago and checked my boil rate. It was 1gal/hr


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Thanks for the replies everyone. .75 to 2 gal/hr is the range so far, with the average being 1'ish.
 
I would say 1 to 1.5 GPH is the norm... mine is 2 GPH (keggle).
% per hour is not really applicable since you'll boil off the same amount whether it be 6 gallons or 16 gallons boiled in the same kettle.
 
I boil off about a gallon per hour, maybe a little less. But I boil 7 gallons on my stove and barely get a boil going.
 
Your boil must be rolling. That means a good fluid transfer via convection. It doesn't need to be jumping out of the surface of the wort. Anything over 15% per hour boil off is excessive for most styles. Pretty much anything is going to suffer once you exceed 20%. The reason is you are producing way to many melanoidin compounds. It will define the beer rather than support it. Melanoids are generally unfermentable, so it will affect apparent attenuation as well

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cjgenever said:
Your boil must be rolling. That means a good fluid transfer via convection. It doesn't need to be jumping out of the surface of the wort. Anything over 15% per hour boil off is excessive for most styles. Pretty much anything is going to suffer once you exceed 20%. The reason is you are producing way to many melanoidin compounds. It will define the beer rather than support it. Melanoids are generally unfermentable, so it will affect apparent attenuation as well

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Click to expand...
Sorry to hijack. That is really interesting... I hadn't considered that part of it.
So, since my boil off is 2 gallons, and I do 5.5 gal batches, beersmith says that's 21.6%.
The only way to change that is to make bigger batches, or slow down the boil?
That could account for consistently high FG's and an undesirable malty taste.
 
I boil off about 1.5 gallons doing a 60 minute boil (6.5 to 5 gallons), and about 2 gallons doing a 90 minute boil (7 gallons to 5 gallons). Using two 1500w heat sticks, and a vigorous rolling boil.
 
acidrain said:
Sorry to hijack. That is really interesting... I hadn't considered that part of it.

So, since my boil off is 2 gallons, and I do 5.5 gal batches, beersmith says that's 21.6%.

The only way to change that is to make bigger batches, or slow down the boil?

That could account for consistently high FG's and an undesirable malty taste.
Click to expand...


Interested to hear the answer to this.

I boil off 1.5g during a 60m boil in a 7.5g pot. I too have been under attenuating.


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cjgenever, I've searched all afternoon and can't find any info supporting your statement.
Can you please site your reference?
 
acidrain said:
Sorry to hijack. That is really interesting... I hadn't considered that part of it.
So, since my boil off is 2 gallons, and I do 5.5 gal batches, beersmith says that's 21.6%.
The only way to change that is to make bigger batches, or slow down the boil?
That could account for consistently high FG's and an undesirable malty taste.
Click to expand...

If you are doing a 60 min boil then you are definitely boiling too vigorously. Melanoidins often have a malty bready taste in the finished brew. The most common boil off figure is one gallon per hour (most recipes are written with this assumption). I usually keep a low roll and really kick it up in the last ten min to remove DMS. that saves on energy.

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cjgenever said:
If you are doing a 60 min boil then you are definitely boiling too vigorously. Melanoidins often have a malty bready taste in the finished brew. The most common boil off figure is one gallon per hour (most recipes are written with this assumption). I usually keep a low roll and really kick it up in the last ten min to remove DMS. that saves on energy.

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Click to expand...

I'd be interested in the citation as well. When I used propane I boiled off 1 gal/hr. With an electric keggle I'm a bit over 2 gal/hr. I don't think I've noticed a significant difference in finished product but did not save any from the same recipe batches for side by side comparison.
 
My boil-off rate is definitely on the higher side, at about 25% per hour... Though this is variable. In the summer (when it is more humid), it is around 20%. In the winter (when it is drier), it is around 30%.

This is the first I've heard of deleterious effects of high boil off rates. The high boil off rates mean that I sparge with a higher volume, which means I extract more sugars during the sparge, which ultimately leads to higher efficiency.

I'd also like to see some sort of references on this claim.
 
In my 9 gal SS kettle with turkey fryer I lose about 1.25 gal an hour. It's got a 14.5" diameter and is about 13.5" tall.
 
I'm also at 2 gal/hr with a 15g megapot from NB (old model). I thought this might be a little excessive, but am not aware of any consequences.

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cjgenever said:
If you are doing a 60 min boil then you are definitely boiling too vigorously. Melanoidins often have a malty bready taste in the finished brew. The most common boil off figure is one gallon per hour (most recipes are written with this assumption). I usually keep a low roll and really kick it up in the last ten min to remove DMS. that saves on energy.

Sent from my SCH-R970 using Home Brew mobile app
Click to expand...

If he can't provide a citation then I'm calling shenanigans.

Kettle design has as huge impact on boiloff and can be independent of boil strength. Back when I did split boils on the stove, I still struggled to reach rolling boil yet still boiled off 20% due to surface area. I still use a fairly wide kettle. Wider kettle = higher boiloff regardless of anything else.
 
I found a citation that supports his claim:

http://homebrewers-haven.com/wpress/how-to-make-beer/melanoidins-101-home-beer-brewers/

The maillard reactions happen in nearly every aspect of brewing, specifically:

Kilning of the grain during the malting process
Drying of the grain during the malting process
Decoction style mashing
Extended boil times
Roaring boil where evaporation rate exceeds 15%
Click to expand...

However, I do take issue with this, since boil off rate is largely affected by equipment, not just how heavy the boil is.
 
max384 said:
I found a citation that supports his claim:

http://homebrewers-haven.com/wpress/how-to-make-beer/melanoidins-101-home-beer-brewers/



However, I do take issue with this, since boil off rate is largely affected by equipment, not just how heavy the boil is.
Click to expand...

Along with humidity. And elevation. And wort gravity. And other factors. Boil strength is only one of many factors in boiloff rate. And setting an arbitrary number of "this is how much you should or shouldn't be boiling off" is problematic.

Will a stronger boil increase maillard formation? Sure. However, I question how significant it is. I also question his claim that "anything suffers above 20% boiloff and you're boiling too vigorously". That's taking leaps of logic that don't include the other factors above.
 
I'm calling bunk on the "excessive boil off rate".
I have a very wide kettle, boil off 2.25 gal per hour.
Get great hot break, great attenuation, & many awards.
 
It's pretty humid in my area so in the summer, I get about 1.25 per hour in my 15 gallon kettle but in the winter its about 1.5 or a bit more.
I use this BIAB calculator and set mine to 1.3 and its worked pretty good for me and my equipment.
 
I also have a problem with the 15% thing. Is this 15% of pre or post boil volume? For 5.5 gal at the end of the boil you're looking at a little under a gallon boil off either way. Also, if I boil off 15% per hour I can never boil the pot dry, can I? I haven't measured but I suspect that for a given kettle and a given heat input under the same environmental conditions I'd boil off a little more per hour doing a 5.5 gal batch vs 11 gallons.
 
I've had almost 25% boil off (1.5 gallons/hour with a 6.5 original boil volume) and have never had any issues with attenuation or caramelization or "bready" characteristics, and can't tell the difference between my beers and beers brewed on other systems with lower rates of boil off, so I call BS. Not saying it's not possible to negatively affect your beer with too rigorous a boil, but to make a rule based on boil off percentage is complete crap.
 
The pod cast that the article was written from is here: http://s125483039.onlinehome.us/archive/bs_melanoidin_7-19-08.mp3
If you want to get to the good parts:
12:15 to 28:40 they talk about flavors.
32: to 46:10 they talk about decoction vs. extended boil vs. ingredients.
48:00 + Boil off rates and at over 15% per hour, will everything taste like a boch? The answer is all equipment is different, but generally speaking, a vigorous boil caused by excessive thermal loading will create undesirable melanoidins.
25% is definitely too much.
20% with undesirable maltiness would indicate too vigorous of a boil.
By controlling the heat, you should be able to control the boil off.
Those guys shoot for no more than 15% per hour.

I use a turkey fryer burner that is not very adjustable.
I have noticed caramelization on the bottom of by BK in the shape of the flame.
Having had problems with what I will call a sickening sweet flavor, I can certainly see how those flavors could have been caused by melanoidins created by excessive thermal loading of the BK.

Listen to the pod cast and decide for yourselves.
I think cjgenever has brought up valid and important info. Thanks!
 
Hamaki said:
I also have a problem with the 15% thing. Is this 15% of pre or post boil volume? For 5.5 gal at the end of the boil you're looking at a little under a gallon boil off either way. Also, if I boil off 15% per hour I can never boil the pot dry, can I? I haven't measured but I suspect that for a given kettle and a given heat input under the same environmental conditions I'd boil off a little more per hour doing a 5.5 gal batch vs 11 gallons.
Click to expand...

It is 15% of preboil. When figuring boil off rate, you always do it as a percent of starting volume. Using a percent per hour figure, you technically can't boil the kettle dry... However, as a brewer, we're only concerned with the boil off rate for one hour, or maybe 90 minutes with some brews, so that little technicality is a non-issue. It does, however, make more sense to measure boil off rates in volume/unit of time (ie. quarts per hour) than a percentage IMO.

And in actual practice, I lose far more volume on the second 30 minutes of my boil than the first 30 minutes, which tells me that the boil off rate is not a linear value.
 
acidrain said:
The pod cast that the article was written from is here: http://s125483039.onlinehome.us/archive/bs_melanoidin_7-19-08.mp3
If you want to get to the good parts:
12:15 to 28:40 they talk about flavors.
32: to 46:10 they talk about decoction vs. extended boil vs. ingredients.
48:00 + Boil off rates and at over 15% per hour, will everything taste like a boch? The answer is all equipment is different, but generally speaking, a vigorous boil caused by excessive thermal loading will create undesirable melanoidins.
25% is definitely too much.
20% with undesirable maltiness would indicate too vigorous of a boil.
By controlling the heat, you should be able to control the boil off.
Those guys shoot for no more than 15% per hour.

I use a turkey fryer burner that is not very adjustable.
I have noticed caramelization on the bottom of by BK in the shape of the flame.
Having had problems with what I will call a sickening sweet flavor, I can certainly see how those flavors could have been caused by melanoidins created by excessive thermal loading of the BK.

Listen to the pod cast and decide for yourselves.
I think cjgenever has brought up valid and important info. Thanks!
Click to expand...

From the posts above, I think many would disagree that 25% is *definitely* too much. Again, I, and others, can't tell a difference in taste between my beers and those done on other systems with lower boil off rates.

My local club just did a Wee Heavy barrel project where 10 of us brewed the exact same recipe, and each batch was tasted before being put into the barrel. I didn't have any issues with attenuation or caramelization, and there was no noticeable taste difference between my batch and the other batches that were brewed, at least not relating to maillard reactions.
 
Converted kegs, 5500 watt elements
~1.15 g/h at 70% duty cycle (gentle rolling boil)
~1.25 g/h at 75% duty cycle (vigorous rolling boil)
~1.40 g/h at 80% duty cycle (leaping boil)
 
max384 said:
And in actual practice, I lose far more volume on the second 30 minutes of my boil than the first 30 minutes, which tells me that the boil off rate is not a linear value.
Click to expand...

Well that is logical. If you don't adjust you heat down through the boil, you are introducing the same amount of heat to a smaller volume of water, which would increase the vigor of the boil, thereby increasing boil off rate.


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TheZymurgist said:
From the posts above, I think many would disagree that 25% is *definitely* too much. Again, I, and others, can't tell a difference in taste between my beers and those done on other systems with lower boil off rates.

My local club just did a Wee Heavy barrel project where 10 of us brewed the exact same recipe, and each batch was tasted before being put into the barrel. I didn't have any issues with attenuation or caramelization, and there was no noticeable taste difference between my batch and the other batches that were brewed, at least not relating to maillard reactions.
Click to expand...

You seem defensive.
Isn't a wee heavy supposed to have some mailard reactions? Recipes I'm seeing are for a 180 minute boil.
Maybe a better test would be with a Blond or a Pale Ale.


Personally, this is kind of an Ah Ha moment... I just ordered two new Banjo Burners.
 
I have a bayou classic propane burner and a 15gal kettle. I boil off about 2.5 - 3 gal in that hour with a pretty aggressive boil.
 

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