OK I'm getting pretty frustrated and could use some advice. I started out using the long metal probe dial thermometers and found that despite calibrating them they were too unreliable. Then I went to a glass, non mercury lab thermometer and I've been using that for a while believing it was pretty accurate. Well now I have some new Blichmann boilermakers and was just down in the kitchen trying to check their accuracy against the lab thermometer in some hot water and low and behold, they were both within 1 degree of each other all the way through the temp spectrum all the way to a full rolling boil maxing out at 219 deg F. So, I also bought a digital probe thermometer as a way to monitor my mash temp at the top of the mash in addition to the Blichmann dial thermometer which will be more towards the middle of the pot, and I thought it would be a good idea to see how it compared to the others. The Digital thermometer read about 4 degrees lower in the 160 degree range and a full seven degrees at boiling, registering exactly 212 at a full rolling boil. Obviously I don't really care about the boiling temp range but a 4 degree difference in the mashing range is in my view significant. Which of these darn things is right?!! Thanks.
Mash temp and Thermometer issues
- Thread starter HBCBrewmaster
- Start date
Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:
Assuming you don't live thousands of feet below sea level, water boils at 212 (or lower if you are in the mountains). If you have your thermometer in water and it reads 219, it is wrong.
If that's the case then I have 3 Blichmann thermometers and a lab thermometer that all read the same thing.
jkarp
Well-Known Member
A man with a watch knows what time it is. A man with two watches is never sure.
Same applies to thermometers and temps.
Get a quality certified lab thermometer and calibrate your Blichmann dials to it.
Same applies to thermometers and temps.
Get a quality certified lab thermometer and calibrate your Blichmann dials to it.
Dschuetz said:If that's the case then I have 3 Blichmann thermometers and a lab thermometer that all read the same thing.
There are other things that can affect boiling point, like pressure or dissolved solutes. This is plain tap water you are testing on, right? Are you letting the thermometer touch the bottom of the pot? Liquid water does not go above 100*C (212*F) under normal circumstances.
Just my opinion, but if a digital thermometer isn't made by Taylor, I don't trust it!
I use a dairy thermometer in the MLT and check temp 10 minutes into the mash and at the end of the mash. I use the Taylor for strike temperature and as a double check for the dairy thermometer. Since I started doing this, my final results have been very consistent and as expected.
Bob
I use a dairy thermometer in the MLT and check temp 10 minutes into the mash and at the end of the mash. I use the Taylor for strike temperature and as a double check for the dairy thermometer. Since I started doing this, my final results have been very consistent and as expected.
Bob
Brewnoob6120
Member
I use a Taylor digital and it is spot on!
cohibamatt
New Member
It is possible to have different temperatures in your mash ton. The top will be colder because it is furthest from the heat. This also means that the bottom is hottest and the middle is so
Where in the middle, of course. I had the same problem with my ton and do a constant recirculation with a pump. I found it takes a about 15 min. to stabilize to the temperature I want. I wouldn't really worry about it too much as long as you are getting the results you want and are able to reproduce them.
Where in the middle, of course. I had the same problem with my ton and do a constant recirculation with a pump. I found it takes a about 15 min. to stabilize to the temperature I want. I wouldn't really worry about it too much as long as you are getting the results you want and are able to reproduce them.
This isn't an issue of mash tun hotspots. He's talking about a 7 degree error in water, not in a mash tun filled with grain.
Well that's exactly the problem; my consistency is inconstant. With my new gear my plan is to recirculate with a march 809 through a home made sarge device and then fly sparge. My hope is that I'll really be able to dial in my temps and have it be consistent throughout the mash.
Thanks
I'm going to check those out. you and others seem to swear by them. Thanks.
So should I be boiling distilled water?
motobrewer
I'm no atheist scientist, but...
i've gone thru 3 taylors, and some of them weren't for brewing. even as a cooking thermometer they are garbage. awful garbage.
the "adjustable" one isn't even adjustable, lol. turn the screw and see what happens. i'll tell you - nothing happens.
the "adjustable" one isn't even adjustable, lol. turn the screw and see what happens. i'll tell you - nothing happens.
wildwest450
Well-Known Member
- Joined
- Dec 27, 2007
- Messages
- 8,978
- Reaction score
- 191
I had much the same experience with several Taylors. They are now residing somewhere in a landfill. The most reliable thermometers are the traceable glass lab thermometers. I have this one and it is go to benchmark when checking/calibrating the others I have:
http://www.carolina.com/product/equ...).do?keyword=745416&sortby=bestMatches&page=1
Brewnoob6120
Member
The first time I used it I checked it at the boiling point of water and it read 212 deg. and my wife is a nurse and checked it against her digital she uses for work and it was dead on with hers so I can't argue with those results much.
Ya I'm leaning toward your position. I have 4 thermometers that all read very close to the same thing and my beers have come out good albeit a bit inconsistent. The inconsistency could easily be due to other factors. It's just frustrating not really knowing what my temps are. It's not that I'm afraid to spend a few bucks to get something I know I can count on but that's just it! How the H E doubble hockey sticks do you know if what you have is giving you a good reading?!
Ideally, but it's hard to imagine that your drinking water has enough dissolved solute to bump its boiling point up a significant amount. May as well give it a try, but I doubt this is your problem.
Ya I'm leaning toward your position. I have 4 thermometers that all read very close to the same thing and my beers have come out good albeit a bit inconsistent. The inconsistency could easily be due to other factors. It's just frustrating not really knowing what my temps are. It's not that I'm afraid to spend a few bucks to get something I know I can count on but that's just it! How the H E doubble hockey sticks do you know if what you have is giving you a good reading?!
It's actually quite easy to test. Boiling distilled water at sea level will be 100ºC. A thick ice slush in the process of melting will be 0ºC. If your thermometers aren't reading those numbers, they're wrong.
Hotspots in a grain bed are a different issue entirely with entirely different solutions, of course, but the first step is to make sure your thermometers are reading properly.
Thermapens are incredibly good, but you certainly pay for them.
Ya I've been eyeballing those Thermapans for a while. I just ordered one. I'm hoping it corroborates the other digital thermometers readings so I can feel confident about calibrating my dial thermometers to them. But if it verifies that my dials are accurate that's not bad either. I figure a $90.00 thermometer with it's reputation ought to be something I can bank on. we'll see. I'll post again once I've had a chance to mess around with it to let yall know what I find. Thanks to everyone for all your input!
feenaughty
Active Member
The one I use at work is a instant read with a probe $189 .water proof can not rember the make but very nice.but I use a $13 at home from walmart one with a probe that I suck in my last mash and was able to close the lid of my cooler tight .
jkarp
Well-Known Member
It's actually not that easy to test. Water's boiling point actually changes with air pressure, not altitude. Barometric pressure can easily change your boiling point by 4 degrees from day to day.
Perhaps you can explain that a bit more...I've always understood that boiling water at higher elevations means a lower boiling point. perhaps that has to do with pressure changes associated with higher altitudes. If that be the case then how do I adjust my expected boil point on any given day? It would seem that a brewer ought to nail that down before trying to make any calibrations. My elevation is 355 ft above sea level which I don't think would have any relevant impact on my boil temperature. This also raises another interesting question about non digital thermometers...Could it perhaps be the case that the temperature reading at boiling given by my lab thermometer is being affected by the change in air pressure? In other words perhaps it's not the temperature at which water boils that's changing but rather the accuracy of my thermometer that is fluctuating with changes in atmospheric pressure? Could such a phenomenon affect lab and dial thermometers and not affect digital ones?
logdrum
Well-Known Member
True, but elevation affects air pressure: for every 500 feet above sea level, water boils at about 0.9F less. (not factoring in barometric pressure) So in cleveland, @ about 900' above sea level water boils at about 211*F. And my cheapie digital Taylor from Target reads that for me.
reference: http://www.hi-tm.com/Documents/Calib-boil.html
-d
That first part is certainly true, and thanks for spotting the over-simplification. That said, 4 degrees is an enormous variation unlikely from simple weather based variation.
The math:
• The boiling point of distilled water is 100ºC at 101.325 kPa.
• At the highest calibrated-to-sea-level pressure ever recorded (108.40 kPa), the boiling point would be 102ºC.
• At the lowest calibrated-to-sea-level pressure ever recorded (during a typhoon, in the middle of the ocean, 87.00 kPa), the boiling point would be 96ºC
So, at the greatest pressure extremes ever recorded, a single location would experience about a six degree variation in temperature.
According to the weather underground's almanac, the lowest and highest barometric pressures over the last year near the OP's location were 99.56 kPa and 103.28 kPa, which gives you a range of 99.47ºC to 100.49ºC. Even these represent extremes, and typical variation during any given week is about half that.
For comparisons sake, average atmospheric pressure here in NYC where I live is right at 101.33 kPa, whereas it is closer to 84.33 kPa in Denver. The day-to-day variation is trivial compared to that.
The punchline here is that it is indeed pressure that predicts boiling (rather than altitude directly), but altitude is an extremely good correlate so long as you don't try to calibrate your thermometer in the middle of a hurricane. If you have a barometer, though, that's certainly a better thing to use to establish your baseline.
Sorry to ramble. Science is fun.
OK I just checked my local weather and my current barometric pressure is 30.38 which according to the above link http://www.hi-tm.com/Documents/Calib-boil.html should give me a boil point of almost exactly 212.79 F (just a hair less exactly) Also, from that source it is apparent that pressure is partly a function of altitude but is also influenced by some other factor not explained. so My assumption, based on that source is that it's not really the altitude that's important but rather the actual barometric pressure. Since I don't know what the pressure was the other day when I did my test I will repeat the test now and see what happens. I would expect an accurate thermometer to read somewhere between 212 and 213. I would accept a less than 1 degree variance in temperature. Be back in a bit with my results.
That first part is certainly true, and thanks for spotting the over-simplification. That said, 4 degrees is an enormous variation unlikely from simple weather based variation.
The math:
• The boiling point of distilled water is 100ºC at 101.325 kPa.
• At the highest calibrated pressure ever recorded (108.40 kPa), the boiling point would be 102ºC.
So, at the greatest pressure extremes ever recorded, a single location would experience about a six degree variation in temperature.
According to the weather underground's almanac, the lowest and highest barometric pressures over the last year near the OP's location were 99.56 kPa and 103.28 kPa, which gives you a range of 99.47ºC to 100.49ºC. Even these represent extremes, and typical variation during any given week is about half that.
For comparisons sake, average atmospheric pressure here in NYC where I live is right at 101.33 kPa, whereas it is closer to 84.33 kPa in Denver. The day-to-day variation is trivial compared to that.
The punchline here is that it is indeed pressure that predicts boiling (rather than altitude directly), but altitude is an extremely good correlate so long as you don't try to calibrate your thermometer in the middle of a hurricane. If you have a barometer, though, that's certainly a better thing to use to establish your baseline.
Sorry to ramble. Science is fun.
not to be nitpickey but I believe you said two things contradictory..."• At the lowest calibrated pressure ever recorded (during a typhoon, in the middle of the ocean, 87.00 kPa), the boiling point would be 96ºC"....and..... "For comparisons sake, average atmospheric pressure here in NYC where I live is right at 101.33 kPa, whereas it is closer to 84.33 kPa in Denver" Unless I misunderstand, how can both statements be true? But your point is well taken that it is not really possible that the pressure alone is creating the discrepency in readings.
Atmospheric pressure is the only thing of the variables we've described here that impacts boiling point. Water boils when its vapor pressure equals the surrounding environment's atmospheric pressure. Elevation does not directly impact boiling point.
But, elevation is a relatively good (though not perfect) correlate for atmospheric pressure if you don't have a barometer. The two are strongly correlated, which makes altitude a good predictor of boiling point, but altitude doesn't directly determine boiling point. If you really want to calculate based on pressure, check your weather report and use this calculator.
It's the old correlation/causation thing. Carrying around a cigarette lighter does not cause lung cancer, but it is strongly correlated to lung cancer.
Daily variation in atmostpheric pressure is kind of like your earlier dissolved solutes question. It does matter, but it can't account for the 7 degree variation you are seeing.
Not to cut in on jkarp, but he's offline now. If he as anything to add or subtract from this, I hope he will.
It looks like you found your own calculator (or you can use the one here), but the amount of variation is small enough that it shouldn't matter unless you are looking to precisely calibrate something. I don't believe that atmospheric pressure can impact temperature readings with either liquid or electric thermometers.
All very good stuff! Thanks. I'm going to repeat me test from the other day with distilled water and newly found knowledge of atmospheric pressure and get back and get back with my results later. stay tuned!
Sorry; that was unclear and I'll change the original post.
When weather services post barometric pressure, they are calibrating it to sea level to remove the amount of variation that is attributed to elevation change. Go to the wunderground.com and check the listing for Denver. Right now, the pressure is listed at 30.33 inHg, pretty much exactly what yours is.
I'm not sure of exactly why they do this, but that number doesn't reflect absolute atmospheric pressure. Instead, 30.33 inHg is how much pressure there would be if Denver were at sea level. The absolute number would be much lower. Meteorologists are tracking weather systems far up in the atmosphere and are interested in the numbers up there. Whether a column of high pressure or low pressure air happens at any given moment to be above Death Valley or Denver doesn't actually change the thing that they are interested in, which is atmospheric pressure at 20k feet (or wherever the heck it is that clouds live).
aww crap. so what you're saying is that the pressure in my kitchen might not be the pressure stated by weather.com...or the wunderground.com for that matter either?...
aww crap. so what you're saying is that the pressure in my kitchen might not be the pressure stated by weather.com...or the wunderground.com for that matter either?...
Nope.
Fortunately, there's a calculator here: http://www.srh.noaa.gov/epz/?n=wxcalc_stationpressure
I tried using that calculator but I need to know my altimeter setting. This seems to be getting too complicated. Would you agree that the difference in pressure that exists at ground level where I am is negligible? After all If can be certain that a temperature reading of 152 F is actually somewhere between 151F and 153 F I'll be satisfied with that. At this point any way. I just don't think a variance of +/- 4degrees is acceptable but +/- 1 degree is.
The "altimeter setting" would (I believe) be the number you are getting for pressure from weather.com. So at 355 ft a weather report of 30.38 inHg is equivalent to 29.99 inHg. Based on that, your water should boil at 212.12 (i.e., almost exactly 212).
To answer your broader question, I certainly agree that this is a level of precision far beyond what is necessary or useful.
At a high-ish elevation or in extreme weather situations it might make a difference, but not for your situation.OK I did a new test with distilled water and tightened up the process a bit using some of the suggestions that you all had. Tomorrow, after I sober up from the Philly Beer Fest I will post my results.
jkarp
Well-Known Member
That depends. C or F?
It is VERY normal to see barometric pressure readings between 28 and 31 in-Hg. Check your local NOAA historical data if you doubt it. Even between those well rounded numbers, water's boiling point will vary 3 degrees Celsius, or over 4 degrees Fahrenheit. Sorry I did not give the scale in my previous post.
Here's a simple online boiling point calculator to play with.
jkarp
Well-Known Member
Exactly. Water is stupid. It is not aware of what elevation it's at. Water held at 30 in-Hg on top of Mt. Everest will boil at 212F.
What does it matter? A boil is a boil. For brewers, as long as the boil temp is > 140F (the isomerization temp of alpha acids), we're just interested in the mechanical process of boiling - churning the wort, evaporation, etc. There's loads of world-class breweries here in CO and none give two thoughts to their boiling point. Mine is around 198F.
Shouldn't be anything different about digital or non-digital thermometers based on pressure. For any thermometer, at sea-level and a local barometric pressure of 30 in-Hg, they should read 212F at boiling in water.
jkarp
Well-Known Member
Call your local TV weatherman. As long as they're not on the air, they gladly give this data out. Just tell 'em you want the local non-elevation adjusted barometric pressure.
Oh, I see. You mean 4 degrees total range (i.e., (210º-214º). I think both the OP and I thought you were suggesting a four degree variation from a mean (212º±4º).
Even still, that seems very high. Do you have a link to the historical data? I couldn't find anything, but I'd be interested to see it. Doing a manual scan over the NOAA data in both my neighborhood and the OP's over the last few years, I found a maximum range on the order of 29.2 and 30.6, which is only 210.8ºF and 213.1ºF. Within that even, those extremes represented unusual days. 95% of days were within 29.6 and 30.3 (211.5ºF and 212.6ºF). But perhaps others aren't so lucky.
jkarp
Well-Known Member
Denver's been above 31 in-Hg and into the low 29s already this year and we're only 2 months in. Maybe our weather's more extreme?
http://www.thorntonweather.com/climatedatayearout.html
