Thermometers and elevations

[7 Slot Brewing]

So as I think about temps more and more, I am trying to figure out exactly what temps I should be mashing at based on my elevation.

So I live at 4200' roughly which means water boils at 204 degrees. Based on candy making experience I know that for every 1000' of elevation I should subtract 2 degrees off the "recipe" temps.

So my question is my recipe states mash should be 154 degrees (sea level) but if I subtract as stated above, I should really be mashing at 146 degrees(4000' elevation)????

And to further this, when I calibrate my thermometer to boiling water, should I put it at 204, or should I put it at 212?

All confused now!

 

[LarryBrewer]

Mash temps should still be the same. It is the reduced boiling temp that you need to compensate for, but even then during mashing that isn't a factor unless you are infusing boiling water to raise the temp of the mash.

Calibrate the thermometer to 204 so it reads correct at all other temperatures.

Your recipes may also need a little extra bittering hops to hit the IBU levels because the boil is cooler, which results in less utilization. My guess is ~3-5%.

 

[Nosybear]

I live at 6,000'. The mash temperatures remain the same but it requires more boiling water to step up temperatures. You want to calibrate your thermometer to 32°F - that temp doesn't vary with altitude or even, very slightly, with barometric pressure. Hop utilization is debatable - my boiling point is down to 199° so is isomerization of the alpha acids as effective here? Lots brew at this (and higher) elevations and lots make good beer so....

Close enough for homebrew.

 

[7 Slot Brewing]

unless you are infusing boiling water to raise the temp of the mash

As in a step mashing correct?

You want to calibrate your thermometer to 32°F -

I was going to do this, so I would go with 154 after this calibration, no changes right?

Figured I was over thinking it....

 

[LarryBrewer]

Yes as in step mashing.

RDWHAHB!

 

[brewtah]

I thought it was 1.2 degrees for every 1000 ft?

 

[Nosybear]

Don't trust that! Once you've calibrated to 32° F, boil a pan of water and take its temperature to determine your boiling point.

 

[LarryBrewer]

If you know you elevation, boiling point should be a fixed figure. Closer to -1.9F / 1000F appears to be the right figure:

http://www.engineeringtoolbox.com/boili ... _1344.html

The OP's number is accurate.

 

[Nosybear]

As an engineer, my pan of water is boiling now.... ;-)

The number calculated is likely correct but I like the hands-on method of calibrating the thermometer to 32° F then measuring my boiling point. It's the experimentalist in me.

 

[brewtah]

So i have a basic thermometer, no calibrations available. my boiling point is 201 F. If i want to mash at say 150, would you increase 4-5%?

 

[LarryBrewer]

So i have a basic thermometer, no calibrations available. my boiling point is 201 F. If i want to mash at say 150, would you increase 4-5%?

Mash temps don't change with elevation. Lower atmospheric pressure at higher elevation reduces pressure on the surface of the water resulting in a lower boiling temperature. Mash temperature has to do with enzyme activation targeted at a specific rage (150-158F), and pressure/elevation does not factor into that.

The only practical difference are the IBUs. Since the boil is not as hot (201 vs 212), the alpha acids don't convert as well during the boil. If you ever moved to a lower elevation and brewed the exact same recipe, it might be 2-3% more bitter.

RDWHAHB

 

[chessking]

Assuming your thermometer is accurate enough, (with all due respect to Heisenberg and his uncertainty principle), you would mash at the temp you want to mash at, in this example 150F. The elevation differential only comes into play when boiling. At higher elevation with reduced air pressure, the water changes from liquid form to gas form (boiling) at a lower temperature. Reduce the air pressure, and the boiling point also reduces. If you reduced the air pressure to zero (complete vacuum), Ice water would boil.
When mashing, hit your target temp and your fine. And unless you are brewing on Mt. Everest, just boil the wort normally. I brew in the Mile High City (Go Broncos) with a boiling point around 202F by my thermometer, and make great beer. Theoretically, hop utilization could be retarded, but not enough in my experience to matter. I believe I read or heard Kai Troester report that hops utilize at boiling or "Near Boiling" temperatures. Good enough for me.

 

[brewtah]

Thanks everyone.

 

[Nosybear]

No, do not change the mash temperature! The active temperature for the enzymes does not depend on altitude or air pressure. The strike temperature remains the same as well - a given mass of water at a given temperature, not boiling, contains the same amount of heat regardless of altitude. The only thing that changes is any time you have to use boiling water. For example, if you're doing a step mash, you'll have to add more boiling water to raise the temperature here in Denver (6000') than in Houston (30'). You can't calibrate your thermometer so take a glass of ice water, put the thermometer in and see what it reads when it comes to rest. If it isn't 32°F/0°C, you will have an offset. If the temperature read/displayed is less than freezing, your offset will be negative - subtract the offset from your desired temperature to get the temperature you read on your thermometer. If the temperature is greater than freezing, add the amount to your desired temperature and, when your thermometer reads the sum, your sample is at the temperature you desire. Simple enough?

By the way, you treat an hydrometer the same way - measure at the calibrated temperature and then know the offset, if any, and apply it to all your gravity readings.

 

[Ozarks Mountain Brewery]

to make this simpler, temperature is temperature, boiling has nothing to do with it, anything can cause liquid to boil slower or faster. the boiling temp does not change the temp settings for your mash