Mash temp disagreement

jay3847

jay3847

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I have an ongoing battle of mash temperature between by digital thermometers and my analog thermometers. My kettle has a thermometer about 3 inches up from the bottom and it might read 160 degrees, but my digital reads 151 even when I stir it REALLY well. So I get my other digital thermometer and it is the same 151. I get the floating thermometer I never use and it reads 160. WTF??!!!

Any suggestions? I'm using a Bayou Classing 8 gallon kettle, and most recently brewing a RIS. Which should I temp use?
 
Stick them all in a glass of ice water. Are they the same there?
 
It's hard to get thermometers reading exactly the same spot. Mash temps vary by a few inches up, down or sideways... especially when reading in the grain bed and in the mash liquor. Seems to me that 9 degrees is a lot, though. I'd see about calibrating the two by holding the probe of the digital right where the heat sensor is in the pot when you have just water in it. That should tell you with some accuracy what's going on.
 
Get a lab grade thermometer and use it to calibrate the others. They're not that expensive.
 
jeffpn said:
Stick them all in a glass of ice water. Are they the same there?
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J A said:
It's hard to get thermometers reading exactly the same spot. Mash temps vary by a few inches up, down or sideways... especially when reading in the grain bed and in the mash liquor. Seems to me that 9 degrees is a lot, though. I'd see about calibrating the two by holding the probe of the digital right where the heat sensor is in the pot when you have just water in it. That should tell you with some accuracy what's going on.
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BOB357 said:
Get a lab grade thermometer and use it to calibrate the others. They're not that expensive.
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Most lab grade are very breakable but not that expensive. Digitals need to be calibrated and all 4 dial style kettle thermometer I use need recalibrated every so often. Have you ever tried the ice water comparison? That is usually required for digital calibration. The old lab thermometers seldom are off, and expect a slight difference between bottom of mash and top. Shouldn't be 9 degrees though.
 
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If you're heating from the bottom and taking the temperature with the digital at the top of the mash, nine degrees isn't that surprising. Do as JeffPN suggests: Ice water is your calibration reference for thermometers, as it is always at freezing. If the thermometers read the same (and it would surprise me if they're off by a degree, let alone nine), then it's a problem with how you're measuring, I suspect you are finding "hot spots" or "cool spots" in the mash.

Or as Thunderwagn suggests, find the reading that works and keep using it.
 
my bottom and top are always different they will eventually even out but not for at least 30 minutes and I don't use heat under the mash, another thing that baffles people is when they heat from the bottom and have a digital probe under the mash, that area is much hotter than the actual mash so you can't rely on that measurement
 
The electronic kitchen thermometers take a bit of time to settle in on a reading. A friend of mine advised me to do the ice water test, as well as the boiling water test. I currently use a kitchen thermometer with a SS capillary and a remote reading device. I try to get into the middle (side to side and top to bottom), then give it some time to settle in on a reading. I had the same experience in my first couple of all grain brews.
Cheers
 
I generally think of my mash in terms of the distinctions of warm (start about 156 degrees and see where it ends), medium (start at 152 degrees and see where it lands) and cool (150 - 148, you know the drill). Seems to work well for me knowing that 1) the temperature will drop over the course of the mash and if I start warm, I'll accomplish the purpose, as beta amylase is denatured, and 2) the temperature in my mash tun is not consistent, it's cooler toward the walls and top than in the middle of the mash, giving me a "step mash" almost by default. Generally I get 80% or more conversion so I'm not unhappy with that, the body of my beers is fairly consistently good, where I want it so this becomes a RDWHAHB situation for me.
 
I use a floating thermomer that I know to be accurate and a electronic remote in the mash. The remote is just to tell me if, and how much, the temperature has dropped. After seeing a 2 or 3 degrees F drop I check the floater to determine if I need to heat it up a few degrees. I found out that the probes with the stainless braided cords are not supposed to be submerged. Ask me how I know you can drown one the first time you use it.

I have a fast reading waterproof digital with a 12" probe and am thinking about drilling a hole in the lid of my kettle and using it instead of the remote. With the BIAB false bottom installed, the end of the probe would be just about dead center of the mash. Just used the false bottom for the first time a couple of days ago, so toying around looking for what works best to control mash temp. Overshot while heating up the first try, so now considering alternatives to recirculating.
 
I have a digital BBQ thermometer that seems to be consistent when I test it, the probe is waterproof and heat resistant so I'm happy with it. Plus the beep when I hit strike temperature is handy.
 
I usually set the beep to occur 10 degrees before strike temp so I don't overshoot, my capillary is made to be submerged (referring of course to the kitchen thermometer...)
 
Great ideas, everyone. I will do the Ice water tests of all the thermometers in cold and hot.

Also need to do controlled tests on when to turn off the burner. I thought I gained 3 degrees from residual heat on the kettle but that didn’t play out this past weekend.
 
jay3847 said:
Great ideas, everyone. I will do the Ice water tests of all the thermometers in cold and hot.

Also need to do controlled tests on when to turn off the burner. I thought I gained 3 degrees from residual heat on the kettle but that didn’t play out this past weekend.
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It also depend on time of year (grain temp) i find in winter i have to turn off burner 2celcius before strike infusion temp thats before immesing grainbag. You get better at feeling your way the more you brew and i say whats a degree or two....o_O:rolleyes:.
 
I have very accurate temp gages .001 accuracy and what you might not realize is I can measure in 5 different places and come up with different temps in the mash every time between the gages, I hate to say it but unless it's a very small batch just dipping a gage in the wort on top doesn't really reflect the actual temp of the whole mash, the only way to get a correct temp is to recirculate and measure the wort only and not inside the grain bed while recirculating, it will surprise you how much differences there are until you reach at least 30 minutes even on recirculation, so don't get too caught up in temperature with hand held devices, just go with your gut and call it good based on past experiences
 
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Here's the results of the great thermometer race: all four within 1 degree of each other when measuring 40 degree, 71 degree, 122 degree and 153 degree water. So, I would agree with Ozark about temp of the wort vs parts of the grain bed. The challenge I see with your comment is that "going with your gut" results from experience. Since I have been doing all grain for a few months, I don't have the experience to have a well educated gut.

With all that in mind, I know that the wort will probably be cooler than the grain since that won't retain heat as well. My process next time will be to use the kettle thermometer since it is sticking right into the grain (with just the nylon bag in the way) and the grain temp is the big issue anyway.

Thank you everyone.
 
BOB357 said:
I found out that the probes with the stainless braided cords are not supposed to be submerged.
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I about killed my cord also. Then got some 1/4” heat shrink tube and covered the top 1/2 of the probe and about 2 feet of the braid. Works great.
 
Group W said:
I about killed my cord also. Then got some 1/4” heat shrink tube and covered the top 1/2 of the probe and about 2 feet of the braid. Works great.
Click to expand...

Great idea. May just try that.
 
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