If the object is quite large, however, or if a lot of them are being made, paint can add considerably to its weight and/or production costs. With that in mind, researchers from Harvard University's Laboratory for Integrated Science and Engineering have created a new lightweight, low-cost coloring technology for both rough and smooth surfaces.

Developed by PhD student Mikhail Kats and his advisor Prof. Federico Capasso, the process involves using a machine known as an electron-beam evaporator to vaporize pieces of metal, by striking them with a stream of electrons. The vapor travels upwards through a vacuum chamber within the evaporator, and collects on the surface of a metallic item placed at the top (if the item isn't metallic, an initial base layer of vaporized metal vapor can first be applied). By repeating this process, multiple layers can be deposited on the item.

What results is an ultra-thin coating. Due to the nature in which that coating scatters reflected light, it appears to the human eye as a given color – exactly which color depends upon the metals used, and the ratios in which they're applied.