Author Topic: Can a boil be too vigorous?  (Read 2647 times)

Offline mcdform

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Can a boil be too vigorous?
« on: February 19, 2015, 05:13:30 AM »
Not sure what happened but took a year of from five gallon brewing.  Made a return, cleaned my burners and found that I'm boiling off a bit over 2 gallons an hour.  The boil is very vigorous, similar to the boil when you forget that you're heating up water to cook pasta.  Lots of bubbling and splashing. 

I know a rolling boil is desirable but is a much more vigorous boil a bad thing?  Will it make my beers darker or is it just making me more inefficient time wise (heating up more water)?
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Offline majorvices

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Re: Can a boil be too vigorous?
« Reply #1 on: February 19, 2015, 12:16:54 PM »
There's no nee3d to boil that vigorously. You just need a gentle roiling boil. The evaporation rate will depend on a lot of different scenarios including the surface are of your open kettle, but 2 gallons an hour is way more than you need. 1/2-1 gallon an hour would be plenty for a 5 gallon batch.

Offline HoosierBrew

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Re: Can a boil be too vigorous?
« Reply #2 on: February 19, 2015, 12:49:50 PM »
+1.  I boil off just over a gallon/hour with no issues at all.
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Offline BrewBama

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Re: Can a boil be too vigorous?
« Reply #3 on: February 19, 2015, 12:56:42 PM »
I think I tend to have too turbulent a boil as well. I need to tone it down.

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rabeb25

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Re: Can a boil be too vigorous?
« Reply #4 on: February 19, 2015, 01:32:25 PM »
You don't want to exceed 20%.

Offline fmader

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Re: Can a boil be too vigorous?
« Reply #5 on: February 19, 2015, 01:34:48 PM »
Crank the burner up to eleven to get your brew boiling, then dial it back to just enough to maintain a rolling boil.
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Offline mabrungard

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Re: Can a boil be too vigorous?
« Reply #6 on: February 19, 2015, 01:51:50 PM »
There are several negatives to excessive boil vigor: excessive wort concentration, bittering contribution is not in proportion to the length of time you can boil, late hop additions are not as effective due to over-volatization.

A nice rolling boil, that you can clearly see is moving the wort and trub in the kettle, is all you really need.
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Offline phunhog

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Re: Can a boil be too vigorous?
« Reply #7 on: February 19, 2015, 02:55:57 PM »
I have always wondered what is most important...the vigor of the boil or the temperature.  I live/brew at sea level but what about brewers in the mountains?  Water boils at under 200 F. at 6000 ft. so obviously their boil is going to be 12 degrees F less than mine.  Does that mean I could get "boil" at 200 degrees as well?  Or is there something important that happens with the actual boiling that isn't necessarily temperature dependent?

Offline Stevie

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Re: Can a boil be too vigorous?
« Reply #8 on: February 19, 2015, 03:25:42 PM »
There's no nee3d to boil that vigorously. You just need a gentle roiling boil. The evaporation rate will depend on a lot of different scenarios including the surface are of your open kettle, but 2 gallons an hour is way more than you need. 1/2-1 gallon an hour would be plenty for a 5 gallon batch.
I get about 1.5 gallons per hour boil off in my keggle. I am very light on the heat adjusting it down to the bare minimum. During the summer, when it is crazy humid, I am closer to 1 gallon.

Offline mcdform

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Re: Can a boil be too vigorous?
« Reply #9 on: February 19, 2015, 05:34:57 PM »
Thanks everyone.  I'll try to tone it down or maybe move my burner down a 1/2" at a time until the boil gets to be the right level.  I brewed a simple recipe to identify establish my system parameters and it seems to have worked in finding out that my boil was too hard.

I estimated about 1.5 gallons/hr and my preboil gravity was right on but it did totally affect the concentration of the wort and I ended up .012 gravity points higher than expected.  I diluted it down some but then that affects the IBU's so we will see what happens. 

There are several negatives to excessive boil vigor: excessive wort concentration, bittering contribution is not in proportion to the length of time you can boil, late hop additions are not as effective due to over-volatization.

A nice rolling boil, that you can clearly see is moving the wort and trub in the kettle, is all you really need.

What happens to the bittering contribution?  I figured they would be higher because of the wort concentration, anything else going on?
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Offline Jimmy K

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Re: Can a boil be too vigorous?
« Reply #10 on: February 19, 2015, 07:19:30 PM »
Thanks everyone.  I'll try to tone it down or maybe move my burner down a 1/2" at a time until the boil gets to be the right level.  I brewed a simple recipe to identify establish my system parameters and it seems to have worked in finding out that my boil was too hard.

I estimated about 1.5 gallons/hr and my preboil gravity was right on but it did totally affect the concentration of the wort and I ended up .012 gravity points higher than expected.  I diluted it down some but then that affects the IBU's so we will see what happens. 

There are several negatives to excessive boil vigor: excessive wort concentration, bittering contribution is not in proportion to the length of time you can boil, late hop additions are not as effective due to over-volatization.

A nice rolling boil, that you can clearly see is moving the wort and trub in the kettle, is all you really need.

What happens to the bittering contribution?  I figured they would be higher because of the wort concentration, anything else going on?
Bittering hop utilization actually decreases as wort concentration increases, so a hard boil could slightly decrease final ibu's.
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Offline Jimmy K

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Re: Can a boil be too vigorous?
« Reply #11 on: February 19, 2015, 07:30:36 PM »
I have always wondered what is most important...the vigor of the boil or the temperature.  I live/brew at sea level but what about brewers in the mountains?  Water boils at under 200 F. at 6000 ft. so obviously their boil is going to be 12 degrees F less than mine.  Does that mean I could get "boil" at 200 degrees as well?  Or is there something important that happens with the actual boiling that isn't necessarily temperature dependent?
I think that some reactions would be just fine, but any that required volatile compounds to be boiled off would suffer. It seems that if water isn't being turned into steam then those compounds are not entering the atmosphere either.

I wonder if having tiny bubbles of stream in the wort affects utilization. Stream at 212F contains a lot more energy than liquid water at 212F.
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Offline mabrungard

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Re: Can a boil be too vigorous?
« Reply #12 on: February 19, 2015, 09:19:58 PM »
If you are boiling to a certain ending volume, you would have to stop the boil earlier. Obviously that reduces the level of isomerization. The other aspect was already pointed out: higher gravity wort reduces bittering contribution.

Yes, isomerization is temperature-dependent. Those living at higher elevations will suffer a reduction in the amount of isomerization their alpha acids will incur due to the wort boiling at lower temperature. There are breweries that use a pressurized boil kettle for the purpose of increasing the boil temperature and increasing the rate of isomerization. The minimum temperature needed for alpha acid isomerization to occur is about 185F. 
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Offline MDixon

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Re: Can a boil be too vigorous?
« Reply #13 on: February 20, 2015, 01:04:53 PM »
If you happen to boil off too much, just add back water to meet the volume or gravity desired. The sugars are conserved, they didn't go anywhere.  8)
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Offline majorvices

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Re: Can a boil be too vigorous?
« Reply #14 on: February 20, 2015, 01:15:23 PM »
If you happen to boil off too much, just add back water to meet the volume or gravity desired. The sugars are conserved, they didn't go anywhere.  8)

Yep, had to do that a zillion times....