Not fade away

Researchers at the Fraunhofer Institute have developed a light dosimeter for assessing the bleaching effects of light on paintings.

The brilliant colours of paintings can fade when exposed to excessive levels of natural and artificial light. Even paper, parchment and textiles can be affected over the course of time. And once a work of art has been damaged by years of light exposure, only painstaking restoration can return it to its former glory.

To help out, researchers at the Fraunhofer Institute for Silicate Research (ISC) have developed a light dosimeter for assessing the bleaching effects of light.

‘Our dosimeter helps museum directors to determine the right time to move an exhibit to a less intensively illuminated display location or, if necessary, even remove it to dark storage vaults,’ explains Dr. Hannelore Römich, head of the LiDo project, which has been sponsored by the EU to the tune of some 750 thousand Euro.

The light dosimeters are Bandaid-like strips affixed to the wall near an exhibit. These strips contain special photosensitive colours that deteriorate faster than the paint used by artists. The dosimeters are collected at regular intervals and the degree of fading is assessed by visual inspection or using special test instruments.

The advantage of the dosimeter over previous measurement techniques is that it gathers light over a longer period of time and thus takes into account variations occurring at the exhibit location, such as seasonal changes in the elevation of the sun, or changes in curtains or artificial lighting.

Along with the ISC branch lab in Bronnbach near Wertheim, two other research institutes are participating in the LiDo project, as well as three museums: the Victoria & Albert Museum in London, the Galleria degli Uffizi in Florence and the Prague National Museum.

Two companies, one in Germany and one in the UK, have already been engaged to market the dosimeter after completion of the field trials.