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-   -   Measuring you mash temps? (http://www.homebrewtalk.com/f36/measuring-you-mash-temps-16818/)

boo boo 11-22-2006 09:28 AM

Measuring you mash temps?
 
I know a man with two watches has two different times so...I use three thermometers when mashing to guage my mash temps, but tend to trust only the alcohol filled glass thermometer for my mash temps. I would like to know of a source for a reliable accurate thermometer that can be had for a reasonable price.

The three I have are the bi-metal one that came with my turkey frier, a cheap ditigal one and my floating glass alcohol filled one. I could try to calibrate mine but want to be sure to have something to compare it too.

Thanks.

zoebisch01 11-22-2006 01:06 PM

I know what you mean. I have three thermometers (two dials and a digital), and did discover that one of them (a small dial accurite) was screwed up. It all depends on what you are willing to pay for one. As far as calibration, it is a little bit of a pain but you can boil a small pot of water and then stick the probe into the (pretty much) 212 F water. It is the only reasonable means aside from buying another thermometer. But what I found out with my screwed up one was that it was bad even after calibrating it. It would cool back down to room temperature and then it was off by quite a few degrees when compared with the other thermometers. Your best bet, imho is a decent digital one because the speed in which they come to measurement temp seems to be much faster than a dial. I bought my 'Big Daddy' (lol) thermometer from homebrewit.com (my local shop doesn't carry equipment) and I couldn't find a long stemmed one anywhere. Hope that helps!

[edit] One thing I forgot, there are adjustments for altitude as well here is a handy dandy table : http://www.hi-tm.com/Documents/Calib-boil.html#tables [/edit]

david_42 11-22-2006 01:40 PM

Probably the most useful way to calibrate a thermometer for mashing is to place a mug with some cheap vodka in a a pot with some water in it. The thermometer goes in the mug with the vodka. When the temperature hits 172F, the alcohol will start boiling off and the temperature won't rise any further until almost all of the alcohol is gone. The water bath helps prevent hot spots that would throw the measurement off.

boo boo 11-22-2006 03:33 PM

I have been playing with the notion of calibrating my existing thermo's but what I really want is a reliable thermostat I can compare the temps to.

Thanks for the replys

Desert_Sky 11-22-2006 04:49 PM

Ive been using a glass labratory thermometer. It was a couple bucks more, and fragile as hell, but from what I hear, its what everyone uses to cal thier digitals

boo boo 11-22-2006 08:53 PM

And what I'll end up buying, also.

perry 11-25-2006 02:39 PM

I've got two of those foot-long dial thermometers with the aluminum shaft from Williams Brewing. They work great; they are fast-reading and easy to calibrate in a glass of ice water- and you can easily hold it in the mash while stirring. They do tend to "spike" occasionally but I guess I just compensate and got used to it...

jp

Baron von BeeGee 11-25-2006 03:00 PM

I've calibrated my digital thermometer (the $25 with a probe type) in an ice bath and boiling water and found it to be exactly accurate at 32F/212F, so I have faith in it.

Aside: I've also noted that in an unstirred mash it's impossible to get an accurate reading anyways and I tend to rely on my strike temp calculation and occasional stirring of my single-infusion mashes (every 20m for just a few seconds). Yesterday I mashed in at 151F (my target) with the probe in the center of the mash. 20m later the probe was reading 158F! I moved it to the edge and got 150F. I stirred and got back to a uniform 151F.

natehilde 11-25-2006 03:07 PM

As far as analog thermometers go, the "liquid-in-glass" expansion thermometer is the most accurate. It is sealed at both ends and thus does not require any adjustment in calibration for elevation pressure differences. The problem with it is the lag time between indication of temperature changes. I like to use the bi-metallic expansion thermometers because of their quick indications. The problem with calibration of this type of thermometer is that you have to calibrate it in the temperature range that you will be using it in. This is very hard to do, unless you have some sort of prime standard for calibration. The next best thing is to calibrate the thermometer at both ends of the scale. Ice water is 32F and water boils at 212F (at sea level). You can use this information to calibrate the thermometer at both ends of the scale. I have never heard of calibrating with alcohol, but that seems to be a reasonable approach.

Just for some background on this information. I am a nuclear power instructor. I teach students about all different types of temperature and pressure indicating devices and calibration of these instruments. IMHO, if it is good enough for neutrons, its good enough for beer.


Just my .02

boo boo 11-26-2006 09:59 PM

Yeah natehilde, I guess it would be.

I have a lab thermo ordered. I like to be as precise as I can when doing any type of measureing.

thanks everyone.


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