How we tested
ThermoWorks recently released an updated version of our favorite instant-read thermometer, the Splash-Proof Super-Fast Thermapen. The new model, called the Thermapen Mk4 (Mark 4), is almost identical to the older model in shape, size, and weight, but has a number of additional features: New sensors allow the display to automatically rotate, wake up, turn off, and illuminate in darker conditions. The Mk4 is more water resistant than the older model and uses a single cheaper, more common AAA alkaline battery instead of the two lithium batteries previously used. ThermoWorks says that as a consequence of the switch, battery life has doubled from 1,500 hours to 3,000.
The Mk4 is sold for $99; ThermoWorks plans to keep selling the older model, now called the Classic Splash-Proof Thermapen, for $79. Curious to see if the improvements were worth having, we bought four Mk4s and tested them against the Classic, using them to take the temperatures of an ice bath and boiling water (to test their accuracy), roast chicken breasts, and caramel sauce; submerging an Mk4 in an 8-quart container of water for half an hour; and having both right-handed and left-handed cooks operate them. We found little difference between the two models in terms of accuracy or speed; both were very precise and read out correct temperatures in 2 to 3 seconds. (One of the Mk4s failed to turn on consistently, so we ordered five additional units to make sure that the problem wasn’t systemic. We’ll continue to monitor their performance, but so far, all the other units have worked great.)
Which Thermapen should you get? While you can’t go wrong with the Classic—our old, reliable favorite, now cheaper than ever before—in the end, we think the Mk4 has a slight edge because of its additional features. The rotating display does make it easier to read the temperature in any position, although it’s a stretch to say that the new Thermapen is therefore as ambidextrous as ThermoWorks claims—the handle is still built for righties, and while the display rotates 360 degrees, the probe itself doesn’t, meaning lefties can’t operate the thermometer at oblique angles.
The extra waterproofing protects the thermometer against more than the occasional splash, ensuring that it’ll survive an accidental drop into a sink full of water, and the backlight made it helpful for grilling at night. Testers particularly liked the new model’s motion sensor-activated automatic sleep/wake function, which means that as long as the probe is out, the thermometer turns on the moment you pick it up; the Classic automatically turns off after 10 minutes, forcing you to close and reopen it when you want it to wake up again. It’s too soon to tell whether the Mk4’s battery life is truly twice as long as the Classic’s, but we’ll keep tabs on the new model in the kitchen and report our findings.