Boiled 3.5 gallons in one hour - is it my elevation?

[dpaola2]

Subject says it all. I live in Lake Tahoe, I'm at about 6,300 ft elevation. I sparged to 6.5 gallons and boiled for an hour. I only got 3 gallons of wort!

Am I crazy? Has anyone else seen that much wort boil off in just 60 minutes?

 

[hopjuice_71]

Wow, thats incredible. This kind of physical chemistry is not my strength, but my gut is telling me that is excessive boil-off. Are you certain you don't have a leak somewhere in your system?

 

[Sammy86]

That seems a bit excessive but lets figure this out. What did you use to boil the wort? Propane? NG? Electric?

My gut feeling is your measurement of pre-boil wort is off. How did you measure it?

 

[tracer bullet]

My gut feeling is your measurement of pre-boil wort is off. How did you measure it?

Agreed. And did you measure at different temps?

It's probably a lot that was boiled off, wow. But it might not be 3.5 gallons.

 

[Plastic Brewkettle]

I'd like to take a guess. Altitude perhaps had little to do with the loss of water. My guess is a high temperature boil. If the boil was excessively vigorous, it could have released an excess of vapor.

 

[PCABrewing]

This isn't your first boil is it?
Have previous boils gone as expected? Is the atmosphere exceptionally dry out there lately?
At your altitude the boiling point is lower (~201 degrees) but I can't understand how that would result in a higher volume lost as vapor? Is your kettle normal diameter for it's volume?

 

[Cyclman]

I am at 6,100 ft., no crazy boil off, and I boil very vigorously.

 

[dpaola2]

Thank you all.

This is my 6th boil, and I have a 10 gallon kettle over propane outdoors. I did boil extremely vigorously, which is a learning moment for me. My kettle has volume indicators which is how I know it was 3.5 gallons lost. I suppose it's possible I mismeasured.

 

[hotbeer]

Your super low humidity compared to everywhere else probably helps might help too. As for temperature of your boil, your wort can't get any hotter than it's boiling temperature for the altitude you are at, however you might could use less heat and not boil so vigorously.

 

[PCABrewing]

Your super low humidity compared to everywhere else probably helps might help too. As for temperature of your boil, your wort can't get any hotter than it's boiling temperature for the altitude you are at, however you might could use less heat and not boil so vigorously.

And save some propane

 

[PCABrewing]

Thank you all.

My kettle has volume indicators which is how I know it was 3.5 gallons lost. I suppose it's possible I mismeasured.

Between old eyes and steam, I find the marks in my kettle challenging to read, especially once the steam is built-up.

 

[cyberbackpacker]

How wide is your pot... a wider pot has a greater rate of boil off versus a narrower kettle. That might be contributing to some of the substantial boil-off too

 

[dpaola2]

Between old eyes and steam, I find the marks in my kettle challenging to read, especially once the steam is built-up.

Fair but I measured it before I started the boil, while sparging. I now think it happened because all of the following factors multiplied:

- Low humidity
- Wide kettle (not tall)
- Very high heat / vigorous boiling

I still think 3.5 gallons in 60 minutes is exorbitant but hey, what else could it be?

 

[dpaola2]

I'm going to conduct a test this week to see if I can reproduce. Science!

 

[ScrewyBrewer]

Fair but I measured it before I started the boil, while sparging. I now think it happened because all of the following factors multiplied:

- Low humidity
- Wide kettle (not tall)
- Very high heat / vigorous boiling

I still think 3.5 gallons in 60 minutes is exorbitant but hey, what else could it be?

Solving for the boiling point of water.

pressure = 29.921*(1-0.0000068753*6300)^5.2559 = 23.7 (inHG)
boiling point = 49.161 * ln(23.7) + 44.932 = 200F

Once water reaches its boiling point, while exposed to atmospheric pressure, it will not get any hotter.

The only other thing that comes to mind would be the air temperature because of its influence on humidity. But I doubt temperature or kettle shape would add much to evaporation.

 

[Jayjay1976]

Did you squeeze the grain bag?

 

[grampamark]

Water boils at a lower temp at higher altitudes but it also boils off faster due to reduced atmospheric pressure. At sea level the pressure, in psi, is 14.7. At 6300 MSL the pressure is only 11.6 psi, assuming standard temp corrected for altitude (about 40°F at 6300]. So, the atmospheric pressure at the OP‘s elevation is <80% of the sea level pressure.

A combination of altitude, kettle dimensions, and miscalculating preboil volume are probably the cause of the OP’s issue.

 

[bracconiere]

Water boils at a lower temp at higher altitudes but it also boils off faster due to reduced atmospheric pressure.

well i live at 4500ft, and it takes FOREVER for water to boil off!

my understanding, is that's true, but only because it allows you to dump more energy into it.....so it's possible to get an even more vigorus boil going....

i've learned to keep at a gente rolling boil by eye, because it saves on gas costs....at least when i still was using propane....

edit: and it hasn't been brought up, so i'll ask...how bad was the hot break boil over?

 

[PCABrewing]

Fair but I measured it before I started the boil, while sparging. I now think it happened because all of the following factors multiplied:

- Low humidity
- Wide kettle (not tall)
- Very high heat / vigorous boiling

I still think 3.5 gallons in 60 minutes is exorbitant but hey, what else could it be?

I was simply supporting your own stated hypothesis from an earlier post " I suppose it's possible I mismeasured" with my experience that it can be difficult under some conditions to measure accurately.
But magic works for me...

As a veteran of six sigma and quality efforts I can tell you there is good reason for evaluating "Gauge R&R" when doing an analysis of failure.

 

[bracconiere]

But magic works for me...

"never believe it's not so!" (i have to turn on the radio and start brew day now....lol)

and figuring things like this out are fun, because of the journey!

 

[PCABrewing]

"never believe it's not so!"

Great tie-in!

 

[grampamark]

well i live at 4500ft, and it FOREVER for water to boil off!

my understanding, is that's true, but only because it allows you to dump more energy into it.....so it's possible to get an even more vigorus boil going....

Well, you’re doing 10 gal batches in a short, wide kettle, straddling two burners on an electric kitchen stove. It works, because you’ve been doing it for years, but it’s not the ideal combination.

I’m at 3300 ft, boiling 7 + gallons on a 30K BTU burner in a relatively tall, skinny, kettle. It only takes about 20 min. to go from mash temp to boiling, and I have to dial the flame way down to avoid boiling off too much. At our city house, which happens to be at the same elevation as our farm, I’m only boiling 4.5 gal in a really skinny kettle, on a 60K burner, and even with 3+ gal of headroom, I have to watch the kettle really closely when the hot break starts to rise.

As I mentioned in my previous post, the OP probably managed to hit a “perfect storm” of combined factors to accomplish an impressive boiloff.

 

[bracconiere]

and I have to dial the flame way down to avoid boiling off too much

it allows you to dump more energy into it.....so it's possible to get an even more vigorus boil going....

so we're in agreement then?


(and actually at first when i was brewing here i did it on propane, and it still took forever to boil off because i'd allready learned to dial back the boil by eye...and it's NG not electric, )

 

[grampamark]

so we're in agreement then?

Well, considering your necessary boil time, you probably aren’t dumping enough energy into it.

 

[bracconiere]

Well, considering your necessary boil time, you probably aren’t dumping enough energy into it.

yeah, not to mention, clean up from the hot break would be a beeatch....

 

[hout17]

How wide is your pot... a wider pot has a greater rate of boil off versus a narrower kettle. That might be contributing to some of the substantial boil-off too

This is something I recently experienced when I changed to a different boil kettle that had much more surface area exposed during the boil. My boil off rate went up quite a bit.

 

[dpaola2]

I did have another note to figure out how to keep the addition of hops from bubbling up like crazy, it was an adventure yesterday. Nonetheless I am excited for this batch, I think it will be my best one yet despite a couple of issues. I can hear it bubbling away as we speak!

 

[doug293cz]

If your boil-off it greater than you desire, it is simply because you are putting too much heat into your kettle while boiling. Once you get to boiling temperature (which as mentioned previously depends on atmospheric pressure) all heat input goes two places:

• Boil-off, at the rate of 970 BTU/lb (8080 BTU/gal) @ 212°F (up to 978 BTU/lb if boiling @200°F [i.e. high altitude])
• Heat lost to the environment. Loss is from kettle walls & liquid surface via convection and radiation, and by conduction thru the kettle support structure.

The first does not vary with environment temp, wind (local air movement), kettle geometry, etc. The second can vary with these variables, the most important being environment temp and wind (air circulation). Humidity does not play a role in vessel heat loss.

So, you need to put a specific amount of heat into the wort to get a specific boil off. You have to add to that all the heat that will be lost to the environment during the boil time, and this will vary depending on env. temp and air movement.

Too much boil-off is not due to altitude or (low) humidity. It's because you are putting too much heat into the kettle.

Brew on

 

[skidmark]

Let's back check this.

What was your actual SG versus expected?

 

[Alanjowitt]

Simmering temperature is the same as vigorous boiling temperature. By boiling vigorously you are introducing more heat than necessary hence increasing evaporation rate. My suggestion is adjust your flame so that you settle on a simmer or very gentle boil.
Do you have a kettle (for tea/coffee) that does not turn off automatically? If so let it boil for an hour and see what happens to the water level.
Otherwise put a pan of water on your stove and simmer for an hour and see how much water you lost. Repeat experiment with element on full power.
Keep an eye on water levels during the above to avoid disaster!