Looking over the artist's shoulder

The color of light Here is the materials science connection. Understanding how pigments such as the chrome yellow and pink madder used by Homer in his watercolor respond to light and/or time can only be achieved using sensitive – preferably nonor minimally destructive – analysis techniques familiar to any materials scientist. Chemical analysis of the watercolor using surface enhanced Raman spectroscopy (SERS) shows that the red and yellow pigments used for the sky have significantly faded over time. A simulation of the original colors casts a rather different hue onto the scene – instead of a bleached out sky, there is a soft orange glow of sunset (Fig. 1b). Raman spectroscopy is a stalwart in the investigation of artworks. The technique is based on the fact that when an incident photon in a laser beam is scattered inelastically by a material, its frequency changes. This unique chemical fingerprint of a material is known as its Raman spectrum1. However, natural organic dyes are easily damaged by light and fluoresce when probed with Raman spectroscopy. Natural organic dyes only started to be replaced with synthetic dyes in the late 1800s and 1900s, so this makes the analysis of many artworks using Raman somewhat limited. SERS, which is a variant of Raman spectroscopy, is not plagued by this problem and takes this kind of analysis to the next level. Pioneered by Richard Van Duyne at Northwestern among others, What could materials science possibly have to do with revealing an artist’s intentions? Intriguingly, art institutions and museums around the world are using a panoply of analysis techniques familiar to any materials scientist to reveal vital and previously hidden information about works of art. We often assume that a painting or statue we are looking at in a gallery or museum is just as it was when the artist created it. But thanks to the rigors of time, artifacts and paintings may deteriorate in subtle or not so subtle ways that can alter our perception of those works, as well as our understanding of their place in history. Or an artist may have reworked or even painted over a piece.