Metal beans to keep coffee warm for hours

You needn't be in a hurry to drink your morning coffee while it's still piping hot. Scientists have developed metal beans that can keep your drink warm for up to five hours.

The beans, called Coffee Joulies, cool down your beverage to a drinkable temperature three times faster than normal, and then maintain that temperature.

They work by absorbing extra thermal energy in the drink when it's too hot, and then releasing that stored energy back into the drink to keep it at an optimum temperature as it begins to cool down, the Daily Mail reports.

While this might seem to go against the laws of thermodynamics, Coffee Joulies contain a 'special non-toxic material' sealed within the beans' stainless steel shells.

A spokesman said: "This material is designed to melt at 140 degrees Fahrenheit, and absorbs a lot of energy as it melts. This is how Joulies cool your coffee down three times faster than normal."

"Once it reaches this temperature, the special material begins to solidify again, releasing the energy it stored when it melted. This is how Joulies keep your coffee warm twice as long."

Using Coffee Joulies couldn't be simpler; all you have to do is add a few to your drink as soon as it's poured.

And you don't have to be a coffee lover to get the most out of the beans - they work in any hot drink, be it tea, hot chocolate or milk.

But the beans - which are due to shortly go on sale in the US with a retail price of $50 for a bag - only work at their best when the cup is insulated with a lid.