Coffee lovers know that there is nothing worse than a cold cup of coffee (unless it is the iced version). Insulated mugs do a half decent job of keeping coffee relatively warm for a short period of time but still many commuters end up drinking lukewarm coffee at their desks to start the morning.

Researchers Klaus Sedlbauer and Herbert Sinnesbichler believe they may have solved the dilemma. They have invented a coffee mug which they say can keep a beverage at its optimum temperature for up to thirty minutes.

Their coffee cup makes use of a material called Phase Change Material, or PCM. PCM is capable of storing large amounts of heat by changing its phase, such as from a solid to a liquid.

In creating their coffee mug, the two German researchers crafted a hollow porcelain shell which they laced with ribbons of aluminum, which is a highly conductive metal. This formed a sort of “honeycomb” structure which they then filled with PCM in its solid state. When a hot beverage was added to the structure the PCM absorbs the heat and its wax like texture becomes liquid. This cools the very hot liquid to its optimal drinking temperature and as the beverage begins to cool naturally the PCM releases the heat it absorbed back into the cup, meaning that the liquid remains at an optimal temperature for up to 30 minutes.

The only downside to the invention is that different drinks have different optimal drinking temperatures. It is generally agreed that beverage like coffee and tea are best enjoyed at about 58C (136.4F) while beer is best enjoyed at about 7C (10.4F). While different mugs utilizing PCM of different types can be created to provide the optimal temperature for each of these different beverages they cannot yet produce a single mug for both hot and cold use. Still, for many, savoring a really good cup of tea or coffee on a regular basis is still a very appealing prospect.

Coffee mugs aside, there could be a multitude of other useful applications for PCM. Researchers are investigating its use with perishable foods to prevent spoilage and even using it on the walls of art galleries and museums to protect priceless works of art in the event of a fire.

PCM is already used in construction, where it can be embedded into walls to provide homes that remain at an optimum temperature. It has also been used in the construction of winter coats, to provide extra warmth on icy days.