Application of the K-edge X-ray technique to map pigments of art paintings: preliminary results

The topographic map of pigments of paintings is a powerful tool for detecting execution techniques, pentimenti and underpaintings hidden to usual imaging diagnostics. Neutron activation autoradiography has provided significant results in few and very important instances. Because of the cost of the nuclear reactor facility needed for a complete painting examination, new technologies to obtain the topographic map of pigments are desirable. Dual-energy radiography can pursue the same goal by tuning the energy gap on the K-absorption edge of interesting elements. The proposed technique is based on the use of quasi-monochromatic beams, with energy below and above the threshold of K absorption of the considered element. In this way two final images are obtained showing the distribution of the specific element and the distribution of all other materials. Preliminary results have been obtained by using samples containing cadmium.