The old alchemist’s dream of turning base metals into gold is still just a dream, but a new technology allows metals to take on different colours without any need for a coating of any kind. A Y Vorobyev and Chunlei Guo of the Institute of Optics at the University of Rochester in New York have shown that femtosecond laser pulses can produce nanostructures that make aluminium appear gold, black or grey, irrespective of the viewing angle.

Other colours can be made, but with some dependence on the angle from which the surface is viewed. It is a low-cost procedure and could find a range of applications.