BBC: Infrared scanning of artwork has been around for a while, but the heat caused by the light source can damage delicate paintings. A new adaption of the scanning technique, reported in Optics Express and called thermal quasi-reflectography (TQR), uses a less-damaging low-power halogen light to generate the IR. A TQR analysis of a 15th-century fresco called The Resurrection by Piero della Francesca showed retouches, unevenness in the painting of a shield, and even changes in the painting technique that do not show up in a near-IR image. More research is needed, say the authors, before TQR can identify pigments to help with restoration rather than just showing that different pigments or techniques were employed.
