Wall paintings at the Casa del Gran Portale, with Giacomo Chiari (GCI) and Francesca Piqué (GCI consultant) collecting samples using a special aspirator. The powder removed by scalpel from the painting is then deposited on a porous filter inside a vial. The sealed vial is then opened in the lab and the powder tested with X-ray diffraction. This technique is very useful when sampling in windy conditions and is an excellent alternative to collecting small powdered samples on pieces of paper. Photo: Giorgio Torraca.