My EVIL Thermometer

[Copernicus]

I brewed a pale ale yesterday, my fourth all grain batch, and was hoping this would be my smoothest brew day yet. My Evil Thermometer ("ET") had different plans.

I heated my mash water until ET said I hit the 165 deg F strike temp. After adding the mash water, ET told me I was around 156 deg F, not my 152 deg F target. I let it mash one hour with ET telling me it stayed between 156 and 154 deg F. Sparged with about 177 deg F water according to the Evil One. The trouble was undeniable when ET told me my boiling wort was 228 deg F. Now I'm no chemist, but...

I decided to calibrate Evil Thermometer today with the following results:
Put ET in an ice bath - 35 deg (3 deg high)
Put ET in boiling water - 224 deg (12 deg high)
Put ET back in the ice bath - 44 deg (12 deg high)

Even my trusty analog thermometer was off:
Analog in ice bath - 24 deg (8 deg low)
Analog in boiling water - 208 deg (4 deg low)

Bottom line
1) I have NO IDEA what temperatures I mashed and sparged at yesterday, and
2) I need a thermometer that...I don't know...tells me the temperature?

 

[Haputanlas]

I had the same problems. Go with the lab thermometers and always use TWO for a sanity check.


http://www.austinhomebrew.com/produ...d=999&osCsid=2b10a692ea68d7bab415bba1d1e668da

This very basic thermometer NEVER fails me.

 

[jasonsbeer]

Forget your thermometer. What's with the crazy purple stove?

 

[Haputanlas]

By the way, I should have mentioned that I had three other thermometers before the lab thermometer (Analog Dial, Digital Dial, and floating thermometer). None of them ever agreed with each other and none would ever calibrate correctly.

EDIT: One more note, you shouldn't use 212 degress F as your calibrated check point for boiling water if you're not at sea level. If you can find your exact elevation, you can make the necessary temp alteration.

 

[JasonInBTR]

I actually did the same thing and got that lab thermometer with my AHS order yesterday. It will at least let me calibrate my other thermometers and hit the right temp for my mash (1st AG coming up soon).

 

[Copernicus]

Forget your thermometer. What's with the crazy purple stove?

It's called the Light Saber Stovetop.

I WISH it looked like that in real life. I think the LED phone/camera flash made it funky in the pic. It's actually just a boring old orange-ish glow.

 

[weirdboy]

I TOLD YOU SO. Well, not you, specifically. But every time thermometers come up I see people recommending these relatively cheap digital thermometers with that style probe. They work great for one or two batches but they go bad quickly if they get even a hint of moisture in them. They are simply not designed with brewing in mind.

I'll stick with my thermapen. Two years now with no problems, and it is super fast and accurate.

 

[Lonnie Mac]

I TOLD YOU SO. Well, not you, specifically. But every time thermometers come up I see people recommending these relatively cheap digital thermometers with that style probe. They work great for one or two batches but they go bad quickly if they get even a hint of moisture in them. They are simply not designed with brewing in mind.

I'll stick with my thermapen. Two years now with no problems, and it is super fast and accurate.

I calibrate everything using my Thermapen. It is good to have and dead accurate. But even still, if you are making great beer and your thermometer is off a few degrees, keep using it and make great beer! Otherwise as they say, a man with two watches doesn't know what time it is.

 

[jackers252]

I just purchased a thermapen Friday because of missing my mash temp on an important recipe.

 

[weirdboy]

I calibrate everything using my Thermapen. It is good to have and dead accurate. But even still, if you are making great beer and your thermometer is off a few degrees, keep using it and make great beer! Otherwise as they say, a man with two watches doesn't know what time it is.

Well when you miss mash temps by 10-20 degrees you will run into troubles. In fact, I realized MY crappy digital oven thermometer was on the fritz when I missed my gravity by like 60% on a batch.

 

[Copernicus]

Yeah, I'm feeling like the thermapen may be in my future. $100 for a thermometer was scaring me away.

 

[Catt22]

The problem with explicitly trusting a Thermapen is that you have no way of knowing if it is accurate or not. Also, the ice cube in water is not likely to be a good benchmark. It needs to be an ice slurry similar to a slushy slurpee or whatever. IOW, very finely crushed ice in just enough water to saturate the finely crushed ice. Be sure to allow several minutes at least for the probe to equalize with the surrounding slurry temperature. It won't happen instantly. Get a high quality traceable glass lab thermometer if you want to know what the temps really are.

 

[weirdboy]

The problem with explicitly trusting a Thermapen is that you have no way of knowing if it is accurate or not.

Well, they are certified. And you still have the ability to check it against known benchmarks and other thermometers. It's not like that magically goes away when you get one.

 

[MetallHed]

From a blog here on HBT:

Easy Thermometer Calibration and Correction
Posted 03-25-2009 at 09:54 PM by ArcaneXor

For my first blog entry, and to commemorate my 1000th post on Homebrewtalk.com, I'm posting these easy instructions on thermometer calibration and correction.

Background:

I am using two thermometers at this point: A floating glass thermometer and a cheap digital probe thermometer from IKEA. I noticed that they read identical temperatures at room temperature, but showed a differential of no less than 14 degrees F at boiling! Needless to say, I was immediately worried about my mash temperatures. I am a partial mash brewer, but grain makes up anything from 50% to 80% of my fermentables, so hitting my infusion temperature is definitely important!

Calibration:

This step is fairly easy. You will need your thermometer(s), some ice and some water. First, you'll want to crush up a bunch of ice, and mix it with a little bit of tap water to create a sort of slushy-type liquid. Pour into a tall glass (like a Pilsner glass), and place your thermometer(s) into that. After waiting about three minutes for the probe to equilibrate, take a reading. Physics dictates that the slushy should be 32 degrees F (0 deg C), so if your readings diverge from that value, record them.

Next, boil some water on the stove and place your thermometer in the boiling liquid, being careful that the probe does not touch the walls or bottom of your boil kettle. Assuming you are located near sea level, physics dictates that water boils at (or very close to) 212 degrees F (100 deg C). If your readings diverge from that value, record them. If you live significantly above sea level, you may want to use Google to locate a calculator or table to identify at what temperature water should boil at your location, and use that value as your reference instead of 212 degrees.

Correction:

Some thermometers have a built-in correction mechanism - refer to your user manual to figure out how to use it. For dial thermometers, it may be as easy as turning a screw. Most thermometers, however, lack a correction function, so you'll have to figure this out by yourself. Excel, or any other spreadsheet software (many of which are available for free online) works very well for this purpose. Basically, we'll be doing a simple linear interpolation through which the range between the observed difference between freezing and boiling temperatures is manipulated so that it equals the known, actual range.

So, open your spreadsheet and label a cell in which you will enter whatever temperature you a trying to achieve (e.g. your target mash temperature). Enter a value in that cell (e.g. 152).
Then, in another cell, enter the following equation:

=observed temp in slushy+((cell with target temperature-32)*(observed temp at boiling-observed temp in slushy))/(212-32)

For instance, assuming the cell you created where you'll enter your target temperature is A8, your observed temp in the slushy is 33 deg F and your observed temp at boiling is 218 deg F, the formula would look like this:

= =33+((A8-32)*(218-33))/(212-32)

You can enter any temperature value you are interested in - once you press enter, the formula will display what your thermometer should be reading at your desired temp. Using the example above, your thermometer will actually read 156.3 degrees when you are at your desired mash temperature of 152 degrees!

It is also helpful to reverse the above calculation so that you can obtain the true temperature given a thermometer reading at any time. All this takes is switching some terms around:

=32+((cell with target temperature-observed temp in slushy)*(212-32))/(observed temp at boiling-observed temp in slushy)

I hope these instructions are helpful, and will assist in you in hitting those mash and sparge temps spot-on without having to buy an expensive, new thermometer.

Cheers, and HAPPY BREWING!

P.S.: In case you ever accidentally submerge a digital probe thermometer under water, you may notice that it will read wildly skewed temperature values afterwards. In most models, that can easily be fixed by placing the probe in a hot oven for a few minutes. This will evaporate the liquid in the probe and essentially reset the thermometer in most models. Also, do a search for "Wort Proofing" on homebrewtalk.com for instructions on how to avoid this happening in the future.

 

[MetallHed]

To fix your ET without buying a new one:

https://www.homebrewtalk.com/f11/remote-probe-thermometer-wort-proofing-26905/

 

[Copernicus]

To fix your ET without buying a new one:

https://www.homebrewtalk.com/f11/remote-probe-thermometer-wort-proofing-26905/

Thanks, MetallHed. I think I will try this solution before shelling out for new gear.