Colour has always been an important part of the art world, with artists using colour to explain complex ideas or highlight important features, or to display logos and crests. One example of a colourful crest is the Incorporation of Hammermen crest.

A beautiful way of using colour in art is the use of stained glass, a technique that has been seen throughout history. A stained glass window is simply an arrangement of different filters, or coloured glass, that create a colour picture – when light shines through the colourful glass, a pattern or image can be seen through the other side.

In the world of advanced engineering, digital cameras use patterns of miniature colour filters so colour photography is possible. Researchers at the University of Glasgow have used techniques that are now being investigated by the camera industry to make filters that are only a few microns in size to make a micro-scale glass window that displays the crest of the Hammermen of Glasgow, seen below. 

The picture of the crest is backlit and was taken using a microscope. The crest is only 0.7 mm in width – about 7 human hairs wide! Unlike stained glass, the crest uses no dyes or pigments – it relies entirely on a natural phenomenon called diffraction to make the different colours.

The crest is made of a thin aluminium film deposited onto a fused quartz plate. The aluminium is pierced with pairs of tiny elliptical holes using electron beam lithography created a patterned mask, and then treated further with a technique called reactive ion etching.

The distance between the holes control the colours that we see due to diffraction, when the light beams change their path when passing through the holes. We think this the smallest crest of any civic institution ever to have been made.

The crest is an example of a metamaterial. Metamaterials do not exist in nature, and are made by humans from metals and insulators to synthesise optical properties that we need for complex systems such as cameras and sensors.

We are very grateful to Shuhao Wu, a PhD student in the James Watt Nanofabrication Centre at the University of Glasgow, for making this wonderful version of our crest.