Changing Metal Color Through Surface Texture

Researchers at the U.K.'s University of Southampton have developed a method of changing the color of gold and silver by etching their surfaces with nanoscale patterns.

The process produces distinctively different colors without using coatings or other chemicals. The key is making surface alternations that create sub-wavelength raised or indented patterns.

The team, a part of the university's Center for Photonic Metamaterials, reported its work in July in the Journal of Optics.

Researcher Kevin Macdonald tells The Engineer that the group has filed a patent application for its process. He says the team uses ion beam milling and electron beam lithography to create nano-patterns in the lab.

At commercial volumes, large surfaces could be stamped from a master template in a technique similar to those used to make CDs and DVDs, according to Macdonald. He adds that the process creates its effects on a single layer and can be varied across a surface. Macdonald envisions initial applications in the jewelry and securities industries.