Over-Engineering the Perfect Mug of Coffee

Yet another use for high-performance computing.

From the annals of Really Important Science comes word of a successful effort to use sophisticated phase-change insulation to keep coffee exactly the right temperature for drinking for as long as 90 minutes.

The “Temperfect” coffee mug is the brainchild of Raleigh-Durham, N.C.-area industrial designer Dean Verhoeven, president of consulting form Ancona Research, Inc., who got some unexpected assistance from a graduating North Carolina State University engineering student to complete the design.

Most insulated mugs have two walls separated by a soft vacuum that insulates the temperature of a liquid inside from the temperature of the air outside.

Maxwell’s design has a third layer of insulation in a third wall wrapped around the inner basin of the mug. Inside is a chemical insulator that is solid at room temperature but melts into a liquid at 140 degrees Fahrenheit.

Verhoeven, a Wisconsin native who had been working for several years on the design and manufacturing requirements of a three-walled, phase-insulated coffee cup for several years and founded the company Joevo to market and manufacture them.

The project got a boost in both planning and publicity after a coincidental meeting between Verhoeven and Logan Maxwell, a recent NC State graduate whose senior design project for the undergraduate College of Engineering was to build a mug that could keep coffee at just the right piping-hot temperature for hours.

The goal wasn’t just to keep coffee hot; the goal was to keep it at a “perfect” temperature of 140 degrees Fahrenheit long enough to allow coffee drinkers to enjoy their beverages slowly.

“I did some research and found that most coffee is served at between 200 F and 185 F, and that coffee can burn you at any temperature above 140 F,” Maxwell said in an NC State newsletter article about the mug. “So we set our ‘ideal’ temperature at 140 F.”who had been working on a similar design and had already worked out how to manufacture a three-walled insulated mug cost effectively.

The solution was an insulator referred to by NC State publicity documents as “material X” because Verhoeven and Maxwell won’t identify it (though they swear it’s non-toxic). The insulator is solid at room temperature but turns to liquid as it absorbs the extra heat of coffee poured into the mug. If the coffee is hotter than 140 F, the insulation melts to liquid, pulling heat out of the coffee to make its conversion possible. As the coffee cools, the insulating material releases heat into it through the inner wall of the stainless-steel mug to keep beverages in it hot as long as possible.

“Phase-change” coffee-mug insulation was patented during the 1960s, but has never been marketed because they are difficult and expensive to manufacture compared to simpler forms of insulation.

A graph mapping the performance of a prototype shows it could keep a cup of coffee at between 128 F and 145 F for as long as 90 minutes.

Voerhoeven said in an email that he had been able to solve the difficulties in manufacturing and, with some help from Maxwell, was able to complete the design of the Temperfect mug.

Maxwell’s participation got the attention of his alma mater, which publicized the project and helped attract enough attention to boost contributions to the KickStarter campaign Verhoeven started to raise the money to manufacture the Temperfect mug. The goal of the campaign was to raise $23,500. So far it has generated $37,000 in commitments with two more weeks to go before funding closes.

There is a a video here explaining the process and pitching the project to KickStarter funders.

Manufacturing will start soon after the KickStarter campaign ends Jan. 1. The first shipments of the stainless steel mugs in a range of colors should arrive at the Raleigh-Durham, N.C. offices of Joevo in March or April.

Maxwell and Verhoeven will complete the final step themselves by inserting the phase-changing insulator and welding shut the inner wall. They’re scheduled to begin shipping by July and will sell for about $40, according to information on the KickStarter page.

Image: Joevo/Maxwell/Verhoeven

Due to errors in the source material and a reporting error, a previous version of this story misidentified Verhoeven’s birthplace, which is in Wisconsin, and the scope of Maxwell’s role in the design. “Logan’s been very helpful in some aspects of the commercialization of the Temperfect mug, particularly its marketing, but was not involved in its development,” according to email from Verhoeven.