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Old 07-18-2012, 10:34 PM   #1
chromephish
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Default Boiling Temperature of Wort 212F or Full Flame?

Probably a simple question but I am gonna test it anyway.
Since you cannot calibrate thermometers in anything but distilled water, I got to thinking. Most beer recipes say how long to boil but not at what temp. Should I boil at 212 F adjusted to sea level or should I blast my burners and crank past 212F and just get the job done ASAP.

Has anyone ever done this? What was the result? I am just finishing my new semi-automated system and our goal is 20 beers for the Michigan vs OSU game in November I probably won't repeat a batch until winter.

Thanks in advance for input.

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Old 07-18-2012, 10:42 PM   #2
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Temperature will not matter. Just get a good rolling boil.

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Old 07-18-2012, 10:48 PM   #3
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Actual temp is irrelevant. Just get a good rolling boil like the last guy said. You want to boil with about the same vigor everytime though so that your boil off rate stays consistent.

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Old 07-18-2012, 10:51 PM   #4
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Once you reach a rolling boil, cranking the gas wide open will not serve any purpose other than wasting gas. The temperature at which water boils is dependent upon atmospheric pressure. If the pressure does not change, the temperature of the boiling water will not change until all of the water evaporates from the boiling. So adding more gas to the burner does not accomplish anything. Once a roiling boil is reached, turn the gas can be until there just enough energy being put into the boil to maintain a rolling boil.

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Old 07-18-2012, 11:16 PM   #5
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Quote:
Originally Posted by chromephish View Post
Probably a simple question but I am gonna test it anyway.
Since you cannot calibrate thermometers in anything but distilled water, I got to thinking. Most beer recipes say how long to boil but not at what temp. Should I boil at 212 F adjusted to sea level or should I blast my burners and crank past 212F and just get the job done ASAP.

Has anyone ever done this? What was the result? I am just finishing my new semi-automated system and our goal is 20 beers for the Michigan vs OSU game in November I probably won't repeat a batch until winter.

Thanks in advance for input.
Boiling temperature does not change. If you're at sea level it's 212F/100C, above sea level the boiling point decreases and below sea level it increases. Increasing the flame on the burner will not increase the temperature of the liquid in the kettle, only its motion and foaming.
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Old 07-19-2012, 02:08 AM   #6
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Thanks everyone for the answers, I have always thought same thing. Being the engineer and 6 sigma Blackbelt guy I am I still have some testing to do. I was researching temperature calibration with some automation engineers at work when we were wiring up my new auberins rtd's I bought. I got these because I was unsure of my Blichman Brewmometers (my partner had complained of swings in his during boil of wort) being accurate. Running my HLT the therm said 212F, however the BK was reading way over the boiling point so I questioned calibration. I then compared the HLT therm to the BK therm after the brew and they read identical.

After looking at some engineering forums on temp calibration it stated it was important to calibrate using distilled water as items in solution will actually allow liquid temp to rise above 212F and even minerals in well water affect this. This is what precipitated question?

So now I have some extra calibrated thermometers and rtd's, because I was paranoid of the issue of one of therms being wrong including one in my Mashtun.

I will calibrate all with a solution 3 parts ice and 1 part water, which is 32 (don't have equipment to test tripoint) and then to a boil at 212. I will boil water, mash some grain and boil/record temp (I am guessing higher than 212 based on what I seen in last batch and on forums (note this was 1st batch with therm in boil kettle, I always just boiled) then double check the calibration.

I am sure taste wise it won't mean anything but hell I am a curious person brewing is a blast, so I may just try a double batch keeping everything constant except boil temp (if I can truly reproduce the higher temp I had seen last batch and didn't really have a calibration issue).

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Old 07-19-2012, 03:26 AM   #7
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It is true that the boiling point depends on pressure and composition (Raoult's Law) such that turning a burner up under a boiling kettle will not increase the temperature but what it will do is put more heat into the mass of boiling wort resulting in a higher rate of evaporation (more vigorous boil). This may or may not be desirable. Certainly a rolling boil is desirable but only up to a point. Also note that if one turns up a flame much of the extra heat simply flows past the kettle (unless it is skirted to prevent this) and so an extra gas flow of x% results in an increase in evaporation of, often, appreciably less than x%.

Also note that the increase in boiling point from Raoult's law consideration is going to be pretty small. Worts may be 12% or so by weight but the molecular weights of the sugars are high (342 g/mol for maltose) compared to 18 for water such that the mole fraction of water in a 12 °P maltose solution is still 99.3% and the vapor pressure reduction and associated increase in boiling point will be small.

Also note that the pressure at the bottom of a foot of wort is 1/30th of an atmosphere (half a psi) higher than at the surface. Thus the boiling point at the bottom of the kettle is higher than at the top and middle. As the wort boils and becomes full of tiny steam bubbles which expand its volume its density is lowered and so is the pressure differential.

What I am getting at here is that if you are recording readings do not expect the temperature to rise smoothly to 212 °F and sit there rock solid. I've seen some pretty squirrely recordings made in boiling wort.

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Old 07-19-2012, 01:09 PM   #8
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The temperature of boiling is hard to adjust unless you have a sealed kettle and can adjust the pressure in the kettle. There is another effect of higher temperature. The rate of Alpha acid isomerization is increased with increased temperature. Conversely, that rate is reduced when the boiling temperature is reduced. This is the reason that hop utilization is reduced for brewers at higher altitudes.

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Old 07-27-2012, 04:47 AM   #9
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Quote:
Originally Posted by ajdelange View Post
It is true that the boiling point depends on pressure and composition (Raoult's Law) such that turning a burner up under a boiling kettle will not increase the temperature but what it will do is put more heat into the mass of boiling wort resulting in a higher rate of evaporation (more vigorous boil). This may or may not be desirable. Certainly a rolling boil is desirable but only up to a point. Also note that if one turns up a flame much of the extra heat simply flows past the kettle (unless it is skirted to prevent this) and so an extra gas flow of x% results in an increase in evaporation of, often, appreciably less than x%.

Also note that the increase in boiling point from Raoult's law consideration is going to be pretty small. Worts may be 12% or so by weight but the molecular weights of the sugars are high (342 g/mol for maltose) compared to 18 for water such that the mole fraction of water in a 12 °P maltose solution is still 99.3% and the vapor pressure reduction and associated increase in boiling point will be small.

Also note that the pressure at the bottom of a foot of wort is 1/30th of an atmosphere (half a psi) higher than at the surface. Thus the boiling point at the bottom of the kettle is higher than at the top and middle. As the wort boils and becomes full of tiny steam bubbles which expand its volume its density is lowered and so is the pressure differential.

What I am getting at here is that if you are recording readings do not expect the temperature to rise smoothly to 212 °F and sit there rock solid. I've seen some pretty squirrely recordings made in boiling wort.
this


pared down to only the most relevant information ---- a given liquid at a given pressure will boil at a specific temperature. once you reach boiling, the temperature of the liquid will not increase no matter how much more heat you blast it with.
adding more heat will make it boil "harder" or faster, which can be good or bad depending on how close you are to hitting your volume.
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