Hands on Review: ThermoWorks Thermapen Mk4 Thermometer

thermapen mk4 review

This review is by Homebrew Finds Contributor Brad Probert.  Brad is an engineer, expert homebrewer and experienced reviewer.  Grab a link to Brad’s website at the end of this review.


Thermoworks Thermapen Mk4

Beer brewing is filled with processes that are based on temperature. Some processes achieve acceptable results with general temperature ranges, but others require specific temperatures where a few degrees hotter or cooler make a difference. But perhaps the most important aspect of temperature accuracy is repeatability. You set up a mash or fermentation process based on expert feedback you read in a book, or just anecdotal advice you get from fellow homebrewers. If it works out to your liking, you want to be able to do it the same way again next time.


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Thermoworks specializes in temperature sensors of all shapes and sizes. They were founded in 1997 and service multiple industries that require temperature monitoring. Specifically well suited for homebrewing, they have quick-responding and accurate digital thermometers that are waterproof rated.

Certificate of Calibration

The Thermapen Mk4 comes with a dated certificate of calibration, with the serial number of the thermometer noted on it. It certifies that your specific thermometer has been calibrated to be accurate at 32F and 212F, within an accuracy of +/- 0.7 degrees F. The digital display can be configured to read out whole degrees, or tenths of a degree. The thermometer senses when you rotate it, and the digital readout rotates along with it, so even if you’re holding it at an off angle, the display stays readable. And enhancing readability, it has a light sensor that automatically backlights the LED in low light situations.

Checking Mashout Temperature

You might be concerned about electronics up close to your wort since brewing is a wet sport. The Thermapen Mk4 is certified to IP67 standard (can handle up to 30 minutes submerged to a 39” depth), so you don’t have to worry about it when it gets splashed, or even if you temporarily lose your grip and have to fish it out. But with the 4.3” long probe only requires the tip to be submerged just 1/8”, you don’t have to get too close to measuring hot mash temps.

Probe Size Comparison to Pencil

The sensor can read temperatures as low as -58F or as hot as 572F. But the plastic body needs to stay between -4F and 122F to avoid compromising it. So don’t get any wild ideas about strapping it to your gas burner to monitor flame temperatures during boil or anything!

It uses a standard AAA battery, which is good for 3,000 hours (without backlight) of temperature measurements. There is no physical on/off switch. It automatically turns on when the probe is folded out away from the body, and turns off when folded back in. If you forget to fold the probe back in, it has an auto-off feature kick in 30 seconds later (which can be customized between 10 – 180 seconds if you want something different).

Thermapen Unboxed

Hands on Review

Upon opening the Thermapen Mk4, the quality of materials/design were readily apparent. The body was made of a durable plastic with a texture to keep it from being slippery when wet, and a nice sky blue color. The digital readout was large and easily legible. The overall size was large enough to be easy to grab, but not so big as to be awkward or clumsy at all.

Thermapen Mk4 Unit

The first thing I did was confirm the calibration was still good. To spot check the accuracy, I made a simple ice bath and confirmed it was reading within the prescribed accuracy- actually right at 32.0 F. I then moved on and used the Thermapen Mk4 in a few different brewing scenarios. The first was during a mash process, and that’s when I discovered the automatic backlight sensor. With the steam coming off the mash, and the shadows cast within the mash tun, it quickly kicked on and made the numbers clearly shine through. This was very nice, after dealing with my old digital temperature sensor that required a flashlight at times to read in similar conditions.

Calibration Check in Ice Bath.  Spot on at 32 deg F,

The temperature response was quick. Notably faster than the digital thermometer I had been using, which took 15-20 seconds for the temperature to finally stabilize. I had always thought it was a direct trade-off between response time and accuracy, but the Thermapen Mk4 showed that wasn’t the case. My old thermometer had a temperature accuracy of +/- 2F and took 20 seconds to stabilize. The Thermapen Mk4 had +/- 0.7F accuracy and took 4-5 seconds to stabilize on its final temperature going from cool basement air temperature (63F) to a fermentation temperature (73F) or to a near mash temperature (130F). So comparing to my old thermometer, the Thermapen Mk4 had the best of both worlds- better accuracy AND faster response.

Most of my brewing equipment now has its own temperature sensor- digital mash controller, digital fermentation temp controller, and Tilt hydrometer. But it’s still nice to have a quick-responding thermometer to do spot checks on temperature. The main use I have for a handheld temperature meter now is for calibrating all of these devices.

Checking Tilt Temperature Calibration – TILT Hands on Review

I’m a data nerd, and detailed record keeper. So it’s frustrating with my Tilt recording a batch fermentation temperature log, and seeing my fermentor controlling to a slightly different temperature. The standard for thermometers is to check the calibration at 32F in an ice bath. But the Tilt’s operating range is above 38F, and the fermentation temperatures I want to be accurate are in the 50 – 75F range. Using the Thermapen Mk4 as my temperature data “master gauge”, I made some 1 gallon water baths in this fermentation temperature range. I then entered temperature corrections into my Tilt app to match the thermometer and did the same with my fermentation controller temperature sensors. Now I know they’ll be tracking together!

Conclusions

The Thermoworks Thermapen Mk4 is beautifully made of high-quality materials and craftsmanship. The features are also of good quality with the rotating display, multi-angle probe adjustment, and backlit readout controlled via a light sensor. And there is performance capability that makes it a great match for homebrewing- fast response time, temperature accuracy, and waterproof rating. It definitely has a price tag commensurate with this quality and these features, but with the importance of temperature through multiple stages of brewing, you might find enough reasons to justify the expense.

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Mentioned in This Review:

More Photos

Calibration Session with BrewJacket Sensors- Hands on ReviewCloseup of Measurement TipProbe in Various Positions
thermapen mk4 review
Thermapen Mk4 in Box
cln_img_9721Back of the box (click to enlarge)cln_img_9724Thew Mk4 features intelligent backlighting.  A version of backlighting was available on the previous Thermapen.  It was an additional cost.  Intelligent backlighting is now standard in every Mk4.cln_img_9725Back of the thermometer.  Note the Serial Number has been removed from this photo.cln_img_9727Side by side next to the previous version – now known as the Classic ThermapenHands Review

cln_img_9733The Mk4 has some additional heft.  Here it is on an American Weigh Gram Scale.  The previous version weighed 94.63 grams.  The Mk4 comes in at 111.42 grams.  About 17 grams heavier.  The AAA batteries probably make up most of that difference.cln_img_9760Here’s the Mk4 in an ice water bath.  This shows a couple things – First, it is reading 32 deg F.  Yay!  Second, you can see the rotating display in action.cln_img_9750The Mk4 is waterproof to the IP66/67 standard

Homebrew Reviews: Homebrew Thermometers

Special thanks to ThermoWorks for providing the units used for evaluation in this review.

By Brad Probert.  Check out Brad’s website – beersnobby.com

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