Coffee Joulies - just the way Goldilocks likes it


March 29, 2011

Coffee Joulies incorporate a phase change material to quickly cool your hot coffee to the "perfect" temperature, and then keep it there

Coffee Joulies incorporate a phase change material to quickly cool your hot coffee to the "perfect" temperature, and then keep it there

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Unless you're someone who drinks their coffee fast, you likely face a bit of a conundrum when it comes to temperature – either you start with it at the perfect temperature but end up with it getting too cold, or you end up with it cooling down to the perfect temperature by starting with it too hot. Two young entrepreneurs, however, have created a product that they claim quickly cools your hot coffee to the right temperature, but then holds it at that temperature twice as long as it would stay there otherwise. Their product is called Coffee Joulies.

Mechanical engineers Dave Petrillo and Dave Jackson grew up together in New Jersey, but have since ended up on opposite sides of the U.S. That hasn't stopped them from collaborating on the design of Coffee Joulies over the past nine months.

Each Joulie contains a proprietary non-toxic phase change material, sealed inside of a polished stainless steel shell. The product is placed in the bottom a coffee mug (or other container), to which the hot java is then added. The secret interior material is designed to melt at 140F (60C), absorbing heat energy from the coffee as it does so. This reportedly allows it to cool coffee three times faster than normal.

Once the Joulie has cooled down past 140 degrees, however, it starts to solidify again, thus releasing the energy it stored while melting. This is what keeps the coffee warm for twice the time of a non-Joulified beverage.

Best results are obtained with a covered, insulated container, while heat-absorbing ceramic mugs offer the poorest performance. Users will have to experiment with different amounts of Joulies and/or with pre-heating them, depending on the size of container and whether or not they cool their coffee by adding cream.

Needless to say, the product does take up room that would otherwise be occupied by liquid – it pretty much comes down to a question of coffee quantity versus coffee temperature.

The two Daves have been making limited numbers of Coffee Joulies by hand, but are currently trying to raise funds to start automated production at an existing silverware plant. They are doing so by offering Joulies in exchange for pledges on the Kickstarter fund-raising website – US$40 will get you five, $100 will get you five and a custom Thermos travel mug, and the $500 Coffee Shop Pack will score you 20 sets of five.

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

Gosh, what a radically important invention!

William Blackburn

Y\'know, I would like to believe that supposedly intelligent people would encourage creativity.

To all you snide little critics: what have you invented? what project have you ever seen all the way through to market?

I hope someday to see these guys bring forth a more complex relevant creation and say, \"Well,we couldn\'t get funding for our real dream because people were too close-minded. So,we made something that the average person could buy as a knick-knack gift and then- well,everything really took off from there!\"

Sometimes, a seemingly stupid goofy toy idea is more profitable and a quicker route to financial freedom than a complex,revolutionary dream to help change the world for the better.

Big or small, good or bad, new ideas will always attract critics who will never create anything.

It\'s always easier to play the critic... than to perform onstage.


\"Heat-absorbing ceramic mugs offer the poorest performance\" says it all, really. Drinking your hot drinks form a ceramic (bone china, please!) cup or mug performs more or less the same function as these beans: the cold cup absorbs the heat from the drink and when the drink is cooler than the cup, the cup returns some heat to the drink. Or you could just drink it when it gets cool enough. Or throw it away and make another, fresh, better tasting cup.



I think it\'s bad wording on Coxworth\'s part that\'s confusing you. The ceramic mugs don\'t absorb and store heat. They rather rapidly conduct it to the outside. Haven\'t you noticed how warm a mug full of hot liquid gets? That\'s heat it\'s losing to the atmosphere, not capturing for later release.

That said, I\'m not impressed by this concept. I\'m guessing they use some kind of eutectic salt for the phase-change material. I\'m more in favor of the \"start at perfect temperature, put in vacuum-insulated mug with lid to keep it there\" technique.


It could be messy retrieving these if they are meant to be reused. Maybe some type of cord or stem to lift them out of the cup when you\'re done? Interesting new use of materials though.


A big fat metal spoon will do the same thing.


The key here is the phase change; by melting, the liquid absorbs far, far more heat energy, per unit mass than it would if it didn\'t. Which is stored as latent heat in the liquid and released as the liquid forms back into a solid.

Look at the specific heat capacity of metals which averages at about 0.5 KJ/Kg, versus the enthalpy of formation of those same metals which averages at 240 Kj/Kg

Also, I doubt retrieval will be too difficult, if you finish your coffee.

Dylan Toms

These beans could be placed in a little bags (like tea bags) that could be easily be removed, rinsed and sterilized in hot water and ready for use the next day. Our culture easily could get their heads around coffee bags to keep your coffee hot. Nice idea.


This would be a great promotional item for coffee distributors. I can\'t see it being a viable product on the consumer market, but it would be something pretty prestigous to receive a bag of those from a catering tradeshow, possibly with each bean branded with a company name and logo.

Maurice Osborne

Phase change.. to difficult.. i can try.. 60 degrees? .. waith.. can it be... candle wax?



No, beeswax. Melts at 60 deg? Check. Edible? Check.

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