Author Topic: Wort vs water boil off rate?  (Read 791 times)

Offline Robert

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Re: Wort vs water boil off rate?
« Reply #30 on: February 12, 2019, 05:53:23 PM »
For a given batch, how good is concentration as an indicator?   I know reduction in volume is not directly proportional to increase in gravity because some extract is lost in precipitation of break material, but has anybody figured out if it's "close enough?"  Or could it serve as a useful alternative indicator of thermal stress on its own, ignoring actual change in volume?
This is what I do. Comparing pre- and post-boil sg's works best for me. Since I use an immersion chiller, measuring pre- and post-boil volumes would be difficult, at best, for me. My process may not be accurate but it's a consistent benchmark for me.
I'm not alone then.  I don't know my actual volumes, because I don't know the exact correction for expansion of the hot (but exactly how hot?) preboil wort, just the fill level of the kettle that works based on experience; the only volume I actually measure is chilled wort (with the IC removed of course!)  Ensuring the correct approximate volume to the fermenter after losses in trub and hops, and being able to calculate brewhouse yield and efficiency, is all that really matters to me.

What I do record of course is pre- and post- boil wort density.   And I know when I got that change down from around 12% in my bad old methods to just 4-6%, the improvement in wort and beer quality was spectacular.   So that's my guide.
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Offline Big Monk

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Re: Wort vs water boil off rate?
« Reply #31 on: February 12, 2019, 05:57:16 PM »
For a given batch, how good is concentration as an indicator?   I know reduction in volume is not directly proportional to increase in gravity because some extract is lost in precipitation of break material, but has anybody figured out if it's "close enough?"  Or could it serve as a useful alternative indicator of thermal stress on its own, ignoring actual change in volume?
This is what I do. Comparing pre- and post-boil sg's works best for me. Since I use an immersion chiller, measuring pre- and post-boil volumes would be difficult, at best, for me. My process may not be accurate but it's a consistent benchmark for me.
I'm not alone then.  I don't know my actual volumes, because I don't know the exact correction for expansion of the hot (but exactly how hot?) preboil wort, just the fill level of the kettle that works based on experience; the only volume I actually measure is chilled wort (with the IC removed of course!)  Ensuring the correct approximate volume to the fermenter after losses in trub and hops, and being able to calculate brewhouse yield and efficiency, is all that really matters to me.

What I do record of course is pre- and post- boil wort density.   And I know when I got that change down from around 12% in my bad old methods to just 4-6%, the improvement in wort and beer quality was spectacular.   So that's my guide.

I’m of the opinion that unless you need the expansion factor to track volumes, it’s really a useless metric.

Cool water in makes way for cool wort in the fermenter and I cool or temperature adjust gravity readings to room temp.

I only use the expansion factors for wort because I measure volume with a SS ruler. It isn’t used for any other calculations except those height based volume ones.
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Re: Wort vs water boil off rate?
« Reply #32 on: February 12, 2019, 08:13:42 PM »
I see your point — it is much easier to measure pre and post boil density (which we do anyway) vs guesstimating volume.

Today’s Exportbier pre boil was 1.052. Post boil it is 1.056. ~7.2% increase in density.


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Offline coolman26

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Re: Wort vs water boil off rate?
« Reply #33 on: February 12, 2019, 08:16:39 PM »
Hell I am at around 4% now and All my grain bills use pils malt. 


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Me too, no matter what it is.


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Offline coolman26

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Re: Wort vs water boil off rate?
« Reply #34 on: February 12, 2019, 08:24:16 PM »
I use the % as a reference. I use gal/hr in actual calculations, but comes out around that %. I laugh at how hard I used to boil.


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Offline Robert

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Re: Wort vs water boil off rate?
« Reply #35 on: February 12, 2019, 08:27:02 PM »



Today’s Exportbier pre boil was 1.052. Post boil it is 1.056. ~7.2% increase in density.


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Between that and your video, I'd say your system is pretty well optimized.   (For some reason my boil moves back and forth too, despite the pattern of heat applied.   I don't understand why,  nor do I feel the need too.  Change in gravity's good, beer's good, that's what I need to know.)
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Offline mabrungard

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Re: Wort vs water boil off rate?
« Reply #36 on: February 12, 2019, 09:19:55 PM »
BTU input and the surface area in the kettle are NOT the components that most directly influence evaporation rate. (OK, you do have to bring the wort to a boil)

All the evaporation equations I’ve seen include a factor that relates how much exchange there is between the high humidity zone (wort surface) and the low humidity zone (the atmosphere). You can boil the stuffing out of your wort, but if there is no exchange with the atmosphere, that steam is going to stay put. If the kettle is fully covered and there is no draft, the only evaporation loss is the steam that leaks around the lid. The amount of water leaving as steam is nearly equal to the condensate that reforms under that lid. That quantity is minor compared to what is lost if the lid is off and there is a breeze blowing across the kettle surface. So don’t forget the impact that atmospheric exchange plays in our boils.
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Offline KellerBrauer

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Re: Wort vs water boil off rate?
« Reply #37 on: February 13, 2019, 12:39:41 PM »
BTU input and the surface area in the kettle are NOT the components that most directly influence evaporation rate. (OK, you do have to bring the wort to a boil)

All the evaporation equations I’ve seen include a factor that relates how much exchange there is between the high humidity zone (wort surface) and the low humidity zone (the atmosphere). You can boil the stuffing out of your wort, but if there is no exchange with the atmosphere, that steam is going to stay put. If the kettle is fully covered and there is no draft, the only evaporation loss is the steam that leaks around the lid. The amount of water leaving as steam is nearly equal to the condensate that reforms under that lid. That quantity is minor compared to what is lost if the lid is off and there is a breeze blowing across the kettle surface. So don’t forget the impact that atmospheric exchange plays in our boils.

I respectfully disagree with the first paragraph.

Regarding the second paragraph:  The fact that ambient temperature, dew point and RH (relative humidity) and lid position also affect the boil-off rate, while obvious, are virtually irrelevant to the point I was trying to make.  These factors are assumed to be relatively constant and equal within ones brewing environment from one brew to the next.

That leads us back to the first paragraph.
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Offline jeffy

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Re: Wort vs water boil off rate?
« Reply #38 on: February 14, 2019, 05:01:01 PM »
I have read all of the posts regarding boil off rate and keep wondering how much af an effect it has on the overall beer.  My method is not so much calculated, but more experiential.  I almost always employ a 60 minute boil and I usually make 10 gallon batches, so for a typical 1.050 cooled wort, I use 15 gallons of water.  I will use more water to make up for bigger grain bills (water absorbed by grain), but I can’t see if there is any other benefit to the amount of boil off other than to dial in your system.
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Offline Big Monk

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Re: Wort vs water boil off rate?
« Reply #39 on: February 14, 2019, 05:09:24 PM »
I have read all of the posts regarding boil off rate and keep wondering how much af an effect it has on the overall beer.  My method is not so much calculated, but more experiential.  I almost always employ a 60 minute boil and I usually make 10 gallon batches, so for a typical 1.050 cooled wort, I use 15 gallons of water.  I will use more water to make up for bigger grain bills (water absorbed by grain), but I can’t see if there is any other benefit to the amount of boil off other than to dial in your system.

Without getting into the weeds, there really isn't any reason to boil the snot out of the wort. I think most would agree with that. People have been becoming aware of things like boil stress on the wort for a little while now. It has long been considered best practice for commercial brewers and it seems to be catching on at the homebrew level as well.

People report good results when decreasing the boil vigor, including better finished malt and hop flavors, etc.
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Offline hopfenundmalz

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Re: Wort vs water boil off rate?
« Reply #40 on: February 14, 2019, 05:32:42 PM »
Surface Area is important for my maple syrup making friends in the club, as the pans are open. Partially closed systems, like a breweries brew kettle with a small diameter stack will be Martin's case.

I once saw the evap rate a homebreeer from Edmonton got in the winter outside it was crazy high as the relative humidity was very low.

This would apply for the maple syrup pan.
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Offline jeffy

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Re: Wort vs water boil off rate?
« Reply #41 on: February 14, 2019, 06:10:19 PM »
I have read all of the posts regarding boil off rate and keep wondering how much af an effect it has on the overall beer.  My method is not so much calculated, but more experiential.  I almost always employ a 60 minute boil and I usually make 10 gallon batches, so for a typical 1.050 cooled wort, I use 15 gallons of water.  I will use more water to make up for bigger grain bills (water absorbed by grain), but I can’t see if there is any other benefit to the amount of boil off other than to dial in your system.

Without getting into the weeds, there really isn't any reason to boil the snot out of the wort. I think most would agree with that. People have been becoming aware of things like boil stress on the wort for a little while now. It has long been considered best practice for commercial brewers and it seems to be catching on at the homebrew level as well.

People report good results when decreasing the boil vigor, including better finished malt and hop flavors, etc.
I have always boiled at what I would call a high simmer, nothing violent, but some occasional rolling activity.  It matches the videos I think I have seen Martin reference.
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Wort vs water boil off rate?
« Reply #42 on: February 14, 2019, 07:31:15 PM »
If nothing else the reduced energy consumption for the “low boil” vs “volcano boil” is a practical reason alone to reduce the boil.  Josh Wiekert presented at NHC that the induction cooktop compared to propane is comparing pennies to dollars. Then from 3.5kw (volcano) to 2kw (low boil) is another 43% less energy.

Technically it makes sense and practically it makes sense.

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« Last Edit: February 14, 2019, 07:38:50 PM by BrewBama »
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Offline Virwill

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Re: Wort vs water boil off rate?
« Reply #43 on: February 17, 2019, 02:55:01 PM »
I'm w/jeffy and BigMonk on the vigor of the boil. I was losing a lot in my initial batches (5-gal. recipes, typically 3-gal. boil) using a high-rolling boil. It occurred to me that if the wort is 212º at an easy boil, the job is getting done and I'm not losing as much volume. I check my level at the tail end of the boil and add (distilled) water to the 3-gal. mark. Not very scientific, granted. I'm thinking of buying an immersion chiller, so might have to shift to measuring the loss after a non-wort 3-gal. boil and adding that volume to my pre-boil volume since displacement would make it impossible to measure the finish. I once made the (apparent) mistake of adding water to the cooled wort in my fermentation bucket to bring it up to the 5-gal. mark. Ended up tasting thin, so I figured that was the problem.

Offline mabrungard

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Re: Wort vs water boil off rate?
« Reply #44 on: February 17, 2019, 03:32:24 PM »
The text and figures for a Zymurgy article on Wort Boiling was handed in last month and it should appear in an issue this summer. The bottom line is that brewers don't necessarily need to boil long or hard to make great beer.
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