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Phase-change mug is claimed to keep coffee hot (but not TOO hot) for hours


December 12, 2013

The Temperfect mug

The Temperfect mug

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Drinking hot beverages can be a tricky business. If you don't want them becoming tepid too quickly, you have to pour them into your mug while they're still too hot. Even then, you're left with a relatively short period in which they're "just right." The designers of the Temperfect mug, however, want to change that. They claim that their mug can keep your drink at the perfect sipping temperature for hours at a time, without using any electricity.

The 16-ounce (473-ml) stainless steel travel mug is a variation on the standard double-wall vacuum flask. In those, insulation is provided by a gap of empty space (from which almost all of the air has been evacuated), between the vessel's exterior and interior surfaces. The tripled-walled Temperfect likewise has a layer of vacuum insulation between its outer and middle walls, but it also features a layer of phase-change material between its middle and inner walls.

Phase-change materials change from one state to another (such as from a solid to a liquid) when exposed to heat, absorbing some of that heat and storing it as energy in the process. As they cool, the materials revert to their former state, releasing the stored heat. They're currently used in products ranging from building materials to temperature-regulating clothing to baby blankets.

In the case of the Temperfect, this means that excess heat from freshly-brewed coffee (as an example) will be absorbed in just a couple of minutes, bringing the beverage down to a hot-but-drinkable temperature. As the phase-change material cools and reverts, that heat is released to flow back through the inner wall and into the coffee, maintaining its "just right" temperature of about 140ºF (60ºC).

Temperfect creators Dean Verhoeven (left) and Logan Maxwell

The mug is being developed by North Carolina State University research assistant Logan Maxwell and engineer Dean Verhoeven, who had previously been working separately on the same basic concept. Verhoeven reportedly found a way around the manufacturing challenges that had stalled other peoples' previous attempts at phase-change mugs.

Much of the secret lies in the choice of phase-change material. While Maxwell can't reveal exactly what it is, he did tell us "It is a waxy material that is totally food safe and non-toxic." In other words, if the inner wall ruptures and the material gets into your coffee, it won't kill you.

Logan and Dean are now raising funds for large-scale production of the Temperfect, on Kickstarter. A pledge of US$40 will get you one, when and if they're ready to go. More information is available in the pitch video below.

If you just can't wait, you might also be interested in buying a pack of Coffee Joulies. They're stainless steel little thingies that contain phase-change material, and they're simply placed in the bottom of an existing mug.

Sources: North Carolina State University, Joeveo, Kickstarter

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

I am guessing tallow but I couldn't find the specific source for temperature. But a food grade paraffin wax could work as well.


If they get this up and running they will sell millions. I wonder if there is a 'reverse' effect to keep icy beverages cool?

The Skud

@ The Skud It is called "ice".


Currently I use a Vacuum mug and it works just fine. Right now my coffee is at 135 Deg after 1.5 hours and they appears to be about 10 oz from 16 left. I typically finish it by about 11:00 with the coffee still hot. I don't mind sipping the really hot coffee when I first pour it in but this product would probably help if you want to get a good kick by drinking a large amount just after making it. This product could also keep you coffee hot longer than a regular vacuum mug if you preheated with boiling water then put your coffee in. The material would absorb more heat than the typical mug. I would be concerned to how well the lining would hold up. Every few months I need to scour the inside of my mug to get it clean.


Thanks MM, I had not gone to the website. Slowburn - DUH! You pedant you.

The Skud

You can use it to keep up a drink cool. Put the mug in a fridge to cool it down, then when you want your drink put it in the mug. This is mentioned on their website.

Matthew Mulvaney

very good idea. Well presented. Promising. I suspect this will take off well. Congratulations Dean and Logan

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