RGB color evolution: A digital tool for monitoring the visual changes of iron oxide pigments irradiated by infrared laser pulses

Abstract

Laser irradiation of powdered iron oxides (goethite and hematite) was performed in order to obtain information about their interaction with short duration near-infrared pulses. Results have shown that under some conditions, Nd:YAG laser provides enough energy to induce fast chemical and structural transformations of the goethite and hematite. This kind of information is of great interest for professionals working with artwork conservation because this technique is used in the conservation of cultural heritage. Depending on the laser's working conditions, glassy (amorphous) material was detected and its presence was related to areas of fast solidification where the energy delivered was enough to melt the powder particles. Color changes wereobserved and quantified by means of an RGB color measurement method developed to show the evolution of each color component.