Boil-Off Rate

I ran an experiment yesterday with my new equipment for all grain brewing.....to determine losses during boil-off and cooling in preparation for my first all-grain brewing sesskion scheduled for tomorrow. This was water only of course.

May 27, 2011

10 gallon SS pot, Bayou Burner
6.5 gal Starting volume
Ambient Temp = 74.6 F

1.3 gal boil loss (55 min)
0.3 gal cooling loss (30 mins) (final temp = 90 F)

I was a bit surprised that the % of boiloff was close to 20%.....only because Beersmith "recommends" a range between 5-15%....but of course what really matters is your own specific set-up.

PLUS.....boiloff should not change based on the volume of starting water (all other things equal).....if I sart with 5 gallons or 10 gallons with the same heat addtiion rate, the total boiloff would be the same either way.

However, the 10 gallon PERCENT boiloff would be half that of the PERCENT boilff in the 5 gallon batch.

So I guess what really matters is that I make sure the total boiloff in beersmith is correct...i.e. adjust the PERCENT input so that I always get a 1.3 gallon boiloff (for a 55 minute boil).......etc

Just wanted to make sure I am not off base here guys.....feedback on your typical boiloff rates would be appreciated.

mgortel said:

I ran an experiment yesterday with my new equipment for all grain brewing.....to determine losses during boil-off and cooling in preparation for my first all-grain brewing sesskion scheduled for tomorrow. This was water only of course.

May 27, 2011

10 gallon SS pot, Bayou Burner
6.5 gal Starting volume
Ambient Temp = 74.6 F

1.3 gal boil loss (55 min)
0.3 gal cooling loss (30 mins) (final temp = 90 F)

I was a bit surprised that the % of boiloff was close to 20%.....only because Beersmith "recommends" a range between 5-15%....but of course what really matters is your own specific set-up.

PLUS.....boiloff should not change based on the volume of starting water (all other things equal).....if I sart with 5 gallons or 10 gallons with the same heat addtiion rate, the total boiloff would be the same either way.

However, the 10 gallon PERCENT boiloff would be half that of the PERCENT boilff in the 5 gallon batch.

So I guess what really matters is that I make sure the total boiloff in beersmith is correct...i.e. adjust the PERCENT input so that I always get a 1.3 gallon boiloff (for a 55 minute boil).......etc

Just wanted to make sure I am not off base here guys.....feedback on your typical boiloff rates would be appreciated.

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Yeah, I think you're on the right track. The % of boil off is meaningless- as you noted that the % will change based on the starting volume. So, stick a figure in there that will give you 1.3 gallons/hour for your system.

The "deadspace" and all that will stay constant also.

In my old system, I boiled off 1 gallon an hour. In my new system, a keggle which is wider, I boil off more like 1.75 gallons an hour. I now start with 7 gallons to compensate for the higher boil off.

Beersmith should change that parameter,

Boil off is dependent upon the diameter of your pot, not how much is in it.

Thanks for reinforcing my conclusions guys....gives me a warm fuzzy feeling inside.....oh wait, that is the beer I am drinking as I prepare to brew!

just want to chime in here and say that I have a large boil off rate....1.75 gals and my pot has a very large diameter also....and yes boil off amount in gallons will be the same regardless of original volume.I have to start with 8 gallons of wort to end up with 5 in the keg. For the longest time I thought I was calculating something wrong, but as it turns out, it was the shape of my kettle. I'm kind of jealous of the people who can start out with 7 gallons of wort.

diameter and boil vigor....both matter. meerrrr

Yea I learned this yesterday when time came to bottle my first brew. I thought I had 5 gallons, but when I transfered to the bottling bucket I only had about 4. I guess I should have tested the boil off rate with my burner.

What's weird is that I hit the OG I was aiming for, dead on? Hm... maybe I read it wrong.

I will do like you did so next time this doesn't happen

mcaple1 said:

diameter and boil vigor....both matter. meerrrr

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Definitely. Environment makes a bit of a difference as well, though the diameter and boil vigor are the biggest factors. I have a tall skinny turkey fryer - 8 gallon total to the brim and about 15" diameter I think, and do a rather low boil for my brews to prevent boilover. I lose about 0.8 gal/hour.

Definitely. Environment makes a bit of a difference as well, though the diameter and boil vigor are the biggest factors.

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I would argue that environment just as big of a factor. I wish there was more research/knowledge out there to help with this. When I brewed a batch this winter in the garage (in lovely cold New England) I had a very high boil-off rate. Ended up with 4 gallons after all was said and done.

After doing a bit of research, the drier the air, the more you will lose. The atmosphere wants to suck up the water, so it will increase your boil off rate. Now, this is something that really effects those up North, as we have cold, dry winters, and warm, humid summers. So there should be quite the adjustment back and forth, but no real math - that I can find anyway - to help calculate what you should be doing based off of the humidity / temperature of the atmosphere.

I'm hoping one day someone with more will-power, brain-power, and time tackles this so I can benefit. Must be some surface area of container to atmosphere and humidity/dew point ratio. Someone please figure this out and publish (or tell me where it is if this has been done.

But yeah, smart tactic by you to test first. Now that you know, and were smart enough to grab the ambient temp, add more wort if it is colder out, less if it is warmer. (If you can look up the humidity of that day, you're doing yourself another favor) I also find the Beersmith boil off rate is too low. I use 15-20% depending on the day.

luke2080 said:

I would argue that environment just as big of a factor. I wish there was more research/knowledge out there to help with this. When I brewed a batch this winter in the garage (in lovely cold New England) I had a very high boil-off rate. Ended up with 4 gallons after all was said and done.

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Interesting! I live in Colorado Springs - basically a high mountain desert. Extremely dry here, and I do have higher boil off rates in the winter - about another quarter gallon or more. So, temp does make a difference (usually about 45 in the garage when brewing in the winter). I wonder how much the humidity (or lack thereof) makes a difference. I agree, would be nice to see someone with more knowledge and research on the subject!

I am confused why people are so extremely worried about boil-off rates though. I mean, why can't you just shoot for a 1 gal/hour boil off rate, and if end up falling short, just top up with some cold water. You will still/should hit your OG. I still have yet to figure out why so many people want to turn this into an exact science when missing your post boil volume by a gallon is something that can be fixed after the boil anyway. I know that hop utilization will change if the wort concentration is higher, but seriously, can someone explain this to me.

By the way, I'm not trying to be a d$%k about this, just confused.

TomStew said:

Yea I learned this yesterday when time came to bottle my first brew. I thought I had 5 gallons, but when I transfered to the bottling bucket I only had about 4. I guess I should have tested the boil off rate with my burner.

What's weird is that I hit the OG I was aiming for, dead on? Hm... maybe I read it wrong.

I will do like you did so next time this doesn't happen

Click to expand...

Wait WHAAAT!? You didn't know you were a gallon short until you were bottling? Why? Don't you have your fermentation volume marked on your fermentation vessel (carboy, BB, etc)?

I am confused why people are so extremely worried about boil-off rates though. I mean, why can't you just shoot for a 1 gal/hour boil off rate, and if end up falling short, just top up with some cold water. You will still/should hit your OG. I still have yet to figure out why so many people want to turn this into an exact science when missing your post boil volume by a gallon is something that can be fixed after the boil anyway. I know that hop utilization will change if the wort concentration is higher, but seriously, can someone explain this to me.

By the way, I'm not trying to be a d$%k about this, just confused.

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If your recipe is based on a 60 minute boil with your hop additions at specific boil times 9of course)......and you end up with TO MUCH water at the end of 60 minutes (i.e. you FG is to low because of the larger volume of water)......your only choices are to continue to boil to remove more water to get closer to your target FG (which results in more hop utilization than you planned on...not a good thing) OR to go ahead and pitch as-is which will result in a lighter beer than you intended.....and may not have the charactere you planned on.

NOW, if you have to high of a FG because you boiled more water off than you planned....then yes...this is simply a matter of adding water after the boil to bring up to your target volume and FG.

Me personally....I like toying with these things....and experimenting and recording the data as part of the hobby and trying to get as close as possible to what I am shooting for....it is part of the fun of home brewing to me. BUT, like you say above....it really isn;t the end of the world....you will still make beer if you are off a little....

Cheers

I was just talking about this with Bob. It's very humid here today (thunderstorms). I'm planning on boiling off less than usual.

In the winter, I boil off more than I do in the summer anyway (we have very very dry winters) but today I think I'll boil off even less than I did on Thursday. I'm going to start with 6.75 gallons today, to end up with 5.25.

mgortel said:

If your recipe is based on a 60 minute boil with your hop additions at specific boil times 9of course)......and you end up with TO MUCH water at the end of 60 minutes (i.e. you FG is to low because of the larger volume of water)......your only choices are to continue to boil to remove more water to get closer to your target FG (which results in more hop utilization than you planned on...not a good thing) OR to go ahead and pitch as-is which will result in a lighter beer than you intended.....and may not have the charactere you planned on.

NOW, if you have to high of a FG because you boiled more water off than you planned....then yes...this is simply a matter of adding water after the boil to bring up to your target volume and FG.

Me personally....I like toying with these things....and experimenting and recording the data as part of the hobby and trying to get as close as possible to what I am shooting for....it is part of the fun of home brewing to me. BUT, like you say above....it really isn;t the end of the world....you will still make beer if you are off a little....

Cheers

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That's kind of my point exactly....I guess if you don't really know your system that well, just shoot for too much boil-off rather than not enough. Assume that you will loose .8-1 gallon per hour, and you will usually end up boiling off more than that in an hour. In the end, top up, and your good. No need for tums.

mcaple1 said:

That's kind of my point exactly....I guess if you don't really know your system that well, just shoot for too much boil-off rather than not enough. Assume that you will loose .8-1 gallon per hour, and you will usually end up boiling off more than that in an hour. In the end, top up, and your good. No need for tums.

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Well, you DO lose some efficiency when you top up with water. I'd much rather get my desired volume from the wort. Even my last runnings may be 1.014 out of the lauter tun. That's definitely higher than 1.000 water.

But, if you need to add water to reach your OG (not your volume), then that's fine.

True...obviously don't have a preboil volume of 4 gallons for a 5 gallon batch...but if we are talking like a quart or two...the resulting inefficiency issue is practically negligible.

mcaple1 said:

True...obviously don't have a preboil volume of 4 gallons for a 5 gallon batch...but if we are talking like a quart or two...the resulting inefficiency issue is practically negligible.

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Oh, I agree! But I do think that hitting your desired OG is far more important than the volume in the fermenter, no matter what. Before blindly topping up, I'd make sure to take an OG reading.

Yooper said:

Oh, I agree! But I do think that hitting your desired OG is far more important than the volume in the fermenter, no matter what. Before blindly topping up, I'd make sure to take an OG reading.

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True true...I guess I'm one of those blind brewers. I never take an OG reading until after I have topped up to 5.25 gallons. I know that may sound stupid, but so far, I have yet to be more than .002 points off target OG going about my methodology this way. I'm sure one day it will bite me in the a$$, but for now, it means less money spent on TUMS and more money spent on HOPS!

Oh..and YOOPER...I'm still gonna take you down in a game of hockey once your leg gets better...I was lying about taking it easy on women.

Yeah I'm one of those for whom Beersmith overestimated evaporation. Ended up with too much water. It was my first effort in this setup though so I will be adjusting accordingly. Makes me want to add a sight glass to the kettle although I may just start with a graduated measuring stick for now.

hops2it said:

Yeah I'm one of those for whom Beersmith overestimated evaporation. Ended up with too much water. It was my first effort in this setup though so I will be adjusting accordingly. Makes me want to add a sight glass to the kettle although I may just start with a graduated measuring stick for now.

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Everyone seems to have issues with BeerSmith with evaporation rate...largely due to the fact that it is a percentage. Use Brewtarget...opensource freeware...works great for me.

mcaple1 said:

Everyone seems to have issues with BeerSmith with evaporation rate...largely due to the fact that it is a percentage. Use Brewtarget...opensource freeware...works great for me.

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I will give it a shot, thanks. How does it predict evaporation by comparison?

I also live in Colorado Springs and have notice a BIG difference with boil-off calculated by BeerSmith and what I am seeing. I boil off about three times more than what BeerSmith is estimating. So between the kettle size and altitude/relative humidity we are seeing big differences. Here is the question... If I adjust my recipe to include more water in my sparging so I get my 5 gallons in the fermentor, what else should I change to make sure I hit the planned O.G.?