LAUSR

Abstract XRF scanners recently have become the most effective tools for analyzing the distribution of pigments on paintings. They are noninvasive and portable and can be used on flat surfaces of notable dimensions. Powerful miniaturized X-Ray tubes combined with more sensitive detectors make it possible to mount instruments on sturdy motorized X,Y devices, and reduce time needed for a scan. The high-resolution results obtained are of the utmost interest for conservators, art historians and conservation scientists. Drawbacks of XRF scanners are the elevated cost and the bulk of the X,Y devices, which makes them more difficult to transport. It is our opinion that the amount of information collected by a scanner is somewhat redundant. Uniform portions of the painting may be treated as a unity. Following this basic idea, a procedure is proposed to combine a high-resolution visible image with compositional measurement carried out on a grid with a much smaller number of points. Different types of images, spatially registered with respect to the visible one, can be used to increase the amount of information available. A computer program, named SmART_scan, statistically combines all available data, and generates false color maps that show the distribution of elements (XRF), or of compounds [XRD or Raman (Tracey et al., 2006)] over the surface. Even so, the collected information still seemed overabundant. For this reason, the program was adapted to work with a limited number of representative points selected by the user. The measuring time was enormously reduced, and the results were reasonably good. The program can be applied retroactively to previously collected data, provided that a good image, the accurate position of the measurements and their numerical results are available. Examples of maps relative to mockups, real paintings, cross sections and three-dimensional objects are shown.