Coffee Joulies are stainless steel beans filled with a phase change material that absorbs heat as it melts – cooling down horrifically hot coffee – and then releases that heat as it re-solidifies – then keeping your coffee warm for longer.
The claim is that the Joulies cool your coffee down 3x faster than normal, and then maintain the “right” temperature up to twice as long, though the latter effect is highly dependent on how insulated your coffee cup is. (Obviously, the more heat the cup releases, the harder it is for the Joulies to work.)
The melting point of the PCM inside of the Joulies is 60C, so ostensibly that’s the “right” temperature they’re aiming for. (Higher temps will cause the Joulies to absorb heat as the material inside melts, until it reaches 60C, at which point the PCM will begin re-solidifying, releasing heat – keeping the coffee at around 60C.) Coffee is typically brewed at around 93C, give or take (unless you’re using a shitty home drip machine), so you’re talking about cooling something down by like 15C three times faster. I’m definitely curious what the effect on the taste of the coffee is – the flavour of coffee changes as it cools, and one of the reasons quality-focused coffee bars don’t pull espresso directly over ice is that it gets sour. (The temp change with Joulies wouldn’t be quite that dramatic, obviously, but I’m wondering if there’s not some effect on flavour.)
If your tongue has been tortured by overly hot coffee one too many times and you don’t think these are voodoo pebbles, fortunately, you can plow your money into the Kickstarter project – $US40 will net you five Joulies of your very own. [Kickstarter via Nick Cho]