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Boil-off Rate

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d40dave

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I read a thread a few weeks ago suggesting a boil-off rate of around 6%. I have looked for this thread but cannot find it. If I could I would have responded to that thread. Anyway I used to set my 5500 Watt controller to 65% and had a boil-off rate of 22% (1.5 gallons). I have tried 3 batches so far with a lower boil-off rate and have achieved a boil-rate of around 10-12% at a setting of 25-30% power, I'm still trying to tweak the process. I do see evaporation but it more like a simmer. I guess that's expected. What I did not expect is that I am seeing gelatinous clumps of something on my wort chiller, there are also smaller chucks on the waterline (wortline) of my brew kettle. Does anybody know what this is and is it normal?

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VikeMan

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What I did not expect is that I am seeing gelatinous clumps of something on my wort chiller, there are also smaller chucks on the waterline (wortline) of my brew kettle. Does anybody know what this is and is it normal?
It's hard to say without seeing it, but it might be hot and/or cold break material, i.e. proteins that have come out of solution. If so, that's both normal and desirable.
 

stickyfinger

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I run my element at 70-80% for 6-16 gallon batches of beer and get around the same rate as you, 1.5-1.7 or so depending. I haven't tried to drop it below that b/c I want an active boil. I've thought about trying a lower boil rate to see if there is a difference but have been satisfied with my beers. did you ever compare a higher and lower boil off rate on a recipe? it would be hard to compare without doing back to back boils with the same wort unless there is a super obvious difference.
 
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d40dave

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It's hard to say without seeing it, but it might be hot and/or cold break material, i.e. proteins that have come out of solution. If so, that's both normal and desirable.
What is hot break? Is it proteins. If it is then maybe it the contributor of my chill haze problems. Next time I'll take a picture.
 

VikeMan

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What is hot break? Is it proteins. If it is then maybe it the contributor of my chill haze problems. Next time I'll take a picture.
It's proteins and polyphenols. When they come out of solution and coagulate together as hot break, they typically don't re-dissolve into the wort/beer. Chill haze is caused by proteins and polyphenols coming out of solution in the finished beer.
 

Tobor_8thMan

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In my experience, the boil off rate depends on the time of the year, the humidity in the air and the boil. May be best to use a spreadsheet and achieve an average boil off amount. Otherwise, you're tweaking on brew day. While an average isn't 100% accurate all-the-time, it's probably close enough. This is known as "dialing in your equipment".
 
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d40dave

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In my experience, the boil off rate depends on the time of the year, the humidity in the air and the boil. May be best to use a spreadsheet and achieve an average boil off amount. Otherwise, you're tweaking on brew day. While an average isn't 100% accurate all-the-time., it's probably close enough. This is known as "dialing in your equipment".
I agree, the last time I set the power level to 25% and came fairly close to 6%. This time I set the power level to 30% because it was freezing out but I over compensated and had to add a quart of water at the end of the boil to achieve what I want to put in the fermenter which is 5 1/2 gallons.
 

Tobor_8thMan

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I now do 75% boil (electric brewing). I make a point of specifying in my recipe instructions.

I also keep track of expected post boil amounts vs. predicted boil amount so I know the difference.

Using 75% boil, for my system, I now obtain consistent results. I achieve an nice rolling boil without crazy evaporation amounts. However, once again, does depend on the time of the year, the humidity in the air, etc.
 

stickyfinger

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Has anyone seen any convincing evidence of a difference in quality on the homebrew scale for varying the boil rate?
 

Tobor_8thMan

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Not me. Prevailing literature calls for "rolling boil". This is to mix everything together (writing in simplistic terms).

Probably others claim "Hey, I made a GREAT beer using no boil!" or, "I boiled for 10 minutes and the beer was GREAT!. Why do you chumps boil for 60 to 90 minutes?"
 

Tobor_8thMan

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I've made some excellent brews. Others have chimed in with their approval. This is nothing I've come up with on my own. It's not me. It's following the input of others and learning from my own and other's problems/mistakes.

IMO, a good rolling boil, at 75%, for 60 minutes (for ale malt) and 90 minutes (for pils malt) works for me.
 

Tobor_8thMan

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There are always "short cuts" in life. Do these work? Maybe. Do these produce desired results in the long term? No! Just think of all the workers around our houses now days. Quickly finish... quickly finish... quickly finish. Is the job done to our satisfaction? Barely. I'd rather the job take a few weeks longer and have the results I desire than a quick finish and be disappointed.

Guess I grew up in different times...
 

michaeltrego

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I typically run my boil kettle (15 gal, 5500w) at 55% with 1.5 gal boil off per hour. I find it amazing that some of you are running at 65+%. If I ran that high it would be an erupting volcano lava show.
 

Vale71

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In my experience, the boil off rate depends on the time of the year, the humidity in the air and the boil.
No it doesn't, neither in your experience nor in anybody else's. You're simply confusing boil rate with evapotranspiration.
 

FswBG

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I remember seeing the thread you are referencing, but took it with a grain of salt. All the books I have read several references that rolling boils are important for melanoid production and fermentation.

Anecdotally, I have brewed familiar recipes on other systems with only a simmering boil and the malt flavor seems to suffer. I’m my mind I rationalize it by comparing to decoction. Obviously it’s a step removed, but the principle is the same. Malt flavor/complexity is an essential element of the boil and adjusting your volume to accommodate boil off isn’t difficult.

To each their own, but I have yet to see any science to prove a low boil brings any benefit. However, I have a feeling some LODO sleuths will prove me wrong here.

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My guess is you read it on a low oxygen brew log. They recommend a low simmer verses rolling boil as well limiting evaporation to 6% - 10% or less of boil volume and control heat stress by limiting boil time to 60-70 minutes.
 
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d40dave

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Here is the thread I was referring to:
 

HardyFool

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If anyone's curious, the boil-off rate for a one gallon batch is approximately .3 gal/hour, a number that's been stubbornly (and thus blessedly) exact since I installed a sight gauge
 

Tobor_8thMan

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No it doesn't, neither in your experience nor in anybody else's. You're simply confusing boil rate with evapotranspiration.
I haven't confused anything. The evaporation rate depends on the boil, time of year, humidity, etc.

I think you misread/misunderstood. Boil off rate aka evaporation rate. I wasn't rating about the boil setting.
 

Vale71

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I haven't confused anything. The evaporation rate depends on the boil, time of year, humidity, etc.

I think you misread/misunderstood. Boil off rate aka evaporation rate. I wasn't rating about the boil setting.
Once again, unless you don't actually boil but wait for water to evaporate spontaneously neither humidity nor time of year play any role at all. Okay, if you brew outside then extreme temperature swings between summer and winter might make a small but noticeable difference, not so much if you brew in a temperature-controlled room indoors.

The only thing determining boil off rate is the power output of the heating system, its yield and any thermal losses your system has during boil which would further decrease its yield.
 

hawaiibrewer

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I've found that the surface area of the boil, ie. 16 in. diameter kettle opening versus 24 in. does indeed impact the boil off rate. As a reference, my 15 gal keggle loses 1/2 gal per 30 min with a rolling boil. Bigger surface area, more loss.
 

Vale71

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I've found that the surface area of the boil, ie. 16 in. diameter kettle opening versus 24 in. does indeed impact the boil off rate. As a reference, my 15 gal keggle loses 1/2 gal per 30 min with a rolling boil. Bigger surface area, more loss.
Do you adjust the power to get the same "appearance" of rolling boil? If that's the case then the increased power output is the reason for the increased boil-off rate, not the surface area.

Energy can neither be destroyed nor created, if you inject the same amount of energy into a system you will get the same result unless the yield (i.e. the losses) change. Some of the results can be counter-intuitive. For example, larger surface area in an open kettle means increased losses due to irradiation from the surface which in turn means lower boil-off rate. That is, unless you adjust the power setting thus changing a major variable making a simple side-by-side comparison meaningless.
 

hawaiibrewer

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I brew with propane....I use my eyes to determine a rolling boil. When I had a large diameter 20 gal kettle, I lost more in boil off then I do with my smaller diameter 15 gal keggle. Use what ever science you want to explain it.
 

Vale71

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To sum it up: you increased the burner's power output and observed a higher boil-off rate. You "chose" to attribute that to the kettle's larger surface area, presumably because that is the theory that on the surface (pun intended) is the most appealing to you, and ignore the obvious fact that you've been putting more energy into the system and that energy has to go somewhere (can you guess where?).
 

hawaiibrewer

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That science is great, but the amount of energy/gas I put into the kettle is actually irrelevant to me since I'm concerned with the amount of wort I end up with to transfer into my fermenter. When I used a larger diameter kettle, I had fewer gallons to transfer. I'm not concerned with btu's needed, kWh used, etc. but rather gallons available to transfer.
 

Vale71

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What's (ir)relevant in your case might not be (ir)relevant to some else. Your claim that "larger surface = larger boil off rate" is in any case wrong and could be misleading to others.
 

JohnDBrewer

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I use propane and keggles. As soon as I get about 4 inches of wort in the bottom of the BK I fire up the propane full blast. I fly sparge so it takes 25 or 50 minutes to fill depending on a 5g or 10g batch. I'm usually boiling when I hit my desired volume. I keep it wide open the whole boil except for short periods to control boil overs. I boil off close to 1.5 gallons per hour. I do this with all my beers to keep the process consistent so I'll be able to replicate the beer on future brews.
 

Tobor_8thMan

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Once again, unless you don't actually boil but wait for water to evaporate spontaneously neither humidity nor time of year play any role at all. Okay, if you brew outside then extreme temperature swings between summer and winter might make a small but noticeable difference, not so much if you brew in a temperature-controlled room indoors.

The only thing determining boil off rate is the power output of the heating system, its yield and any thermal losses your system has during boil which would further decrease its yield.
Nope! Boil rate, humidity, time of year all factor into the boil off amount. Even as something as simple as a coffee pot sitting on the warming plate loses more volume when there is less humidity in the air than when the air is humid.
 
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