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Old 12-29-2011, 07:14 PM   #1
y2jrock60
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Default Problems measuring mash temp

I brewed my first batch of beer last week after a two year hiatus. My buddy and I finally invested into some new equipment. The brewing kit we purchased advertised that it came with a thermometer on the box, it turned out to be a sticker style thermometer for the fermenter. It was late at night so the only place that was open was a small grocery store down the street where we picked up a cheap meat thermometer. It did the job, we were able to take accurate temperature readings, but it took forever for the needle to rise and it was pain holding a small thermometer in the mash and strike water for extended periods of times. Before we made a second batched we picked up a digital thermometer with a probe. It seemed to work really well and gave us fast and accurate measurements of our strike water with ease. However, when we dumped our strike water into our mash tun and added grain the thermometer went hay wire. I understand that different parts of the mash tun may be off by a degree or two, but we were getting readings with over 10 degrees of difference. We ended up adding a little hot water because we thought we were too low, then we a small amount of cool water because we thought we were too hot. We were unable to get a consistent reading after about 5 minutes. That's when we decided to say screw it and shut the mash tun and left it where is was. We used the same thermometer to heat up our sparge water to 168 degrees without a problem. For some reason it refused to work in the mash.

Does anyone know what is going on with our thermometer? I would like to get accurate mash measurements because I like experimenting with the effects of different temperatures. I wanted to mash at 155 to obtain a thicker sweeter beer, but I have no idea what my mash temperature was after all the failed adjustments. Our OG with dead on the mark, so I know we extracted enough sugars, but I'm not sure at what temperature. I should have probably just added my strike water at the suggested temperature and put the thermometer aside. Our first batch was within one degree of our predicted temperature. It kind of irritates me though that I can't get a good reading with an expensive thermometer.

Does anyone have any suggestions or similar experiences?

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Old 12-29-2011, 07:36 PM   #2
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I can't help you determine why your thermometer went crazy in the mash, but I use this one from Thermoworks and it works great:

Amazon.com: RT600C Super-fast Water-resistant Digital Pocket Thermometer: Kitchen & Dining


It's $19, splash proof, and offers fast temp readings of only a few seconds.


Rev.

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Old 12-29-2011, 07:37 PM   #3
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A couple things can be going on.
1. You could not be mixing the grain enough with the strike water. If that is the case then you will get hot and cold pockets in your mash tun. Normally I stir in the grain for a minimum 5 minutes.
2. Your thermometer could be off. Can you calibrate it? If it is off you should be consistently off. I would think your problem relates more to 1 than it does 2.

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Old 12-29-2011, 08:19 PM   #4
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Quote:
Originally Posted by Rev2010 View Post
I can't help you determine why your thermometer went crazy in the mash, but I use this one from Thermoworks and it works great:

Amazon.com: RT600C Super-fast Water-resistant Digital Pocket Thermometer: Kitchen & Dining


It's $19, splash proof, and offers fast temp readings of only a few seconds.


Rev.
+1, I have this same one and I like it a lot, pretty quick readings.

I also wonder if you just need a little more mixing/equilibration time. Did you pre-heat the mash tun? I mix for a full 5 minutes then let it sit for another 5 or so before taking a reading.
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Old 12-30-2011, 02:38 AM   #5
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I put about a gallon of boiling water into the mash tun about 20 minutes before I mashed. I probably stirred the grain longer than 5 minutes due to the temperature discrepancies. I'm going to try using it again with the next mash, it works well in plain water. If it goes haywire again I will just throw it aside and put my faith in the strike water calculators. They seem to be pretty accurate, usually within a degree. It kind of sucks though, I'm kind of anal and scientific in my brewing process, I like to be precise as possible.

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Old 12-30-2011, 04:57 AM   #6
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If you're stirring your mash anyway, rig up a way to lash that meat thermometer to the side of your tun. You won't need fast readings, and you can pull it off when you're ready to close 'er up.

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Old 12-30-2011, 07:48 AM   #7
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I mash in a cooler. I have a glass floating thermometer that I stuff into the mash and cover. Every 15 min I stir and take a quick reading and replace the thermmeter deep in the mash.

I use a fast reading digital one to determine the strike water temp, then I switch to the glass one and leave it in the mash ton.

Digitals may be water resistant, but not water proof. Keep the probe end where it attaches to the cable out of the water.

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Old 12-30-2011, 08:39 AM   #8
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Definitely had this happen to me when I was doing a really thick mash (~1.25 qts/lb) in my kettle with a bag that was too small. So I got some bigger paint straining bags for my grain, got some bigger pots, increased my mash ration to 1.75 qts/lb, and got the weldless brewmometer from blichmann, and now I can control my mash temperature like a champ.

At first I used floating thermometers with my thick mash, but they seemed inaccurate and slow...but the main problem was the mash being too thick and the grains being too crowded. I then used to use one of those digital thermometers with the teflon cable and the probe, but apparently you aren't supposed to get the connection wet, which made my thermometer go haywire and then break. Now it's back to the trusty floating thermometer in one pot and the blichmann in the other one. The floating thermometers work well as long as your mash isn't too thick and you give it a bit of stirring every 15 min or so as C-Rider said.

I also recently bought one more thermometer ( Amazon.com: Traceable Long-Stem Thermometer: Industrial & Scientific ) and used a drill with a step bit to make a small hole in the lid so I can monitor the temperature when mashing and when cooling the wort after the boil.

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Old 12-30-2011, 11:38 AM   #9
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Quote:
Originally Posted by y2jrock60 View Post
I put about a gallon of boiling water into the mash tun about 20 minutes before I mashed. I probably stirred the grain longer than 5 minutes due to the temperature discrepancies. I'm going to try using it again with the next mash, it works well in plain water. If it goes haywire again I will just throw it aside and put my faith in the strike water calculators. They seem to be pretty accurate, usually within a degree. It kind of sucks though, I'm kind of anal and scientific in my brewing process, I like to be precise as possible.
Your thermometer doesn't go haywire in the mash tun and then magically fix itself when you test it in water. To put it simply, it is difficult to mix the mash thoroughly enough to get even temperatures throughout. Keep stirring until it seems close and then put the cover on and forget it.
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Old 12-30-2011, 12:07 PM   #10
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You probably got the connection wet, as stated earlier....this busts the thermometer...search for waterproofing your thermo....you'll have to bake the probe (with plastic outside the oven) to dry it out first.....bobbym has an awesome writeup on all of this somewhere...it's a pretty common issue

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