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Presenting results from this imaging technique in meaningful ways requires mathematical manipulation. In this case, three images recorded at invisible wavelengths of 1000 nanometers (nm), 1300 nm, and 1660 nm are displayed as blue, green, and red, respectively, to make a false-color image. Next, two other images at 1600 and 1449 nm were subtracted to create a difference image. This difference image was made partially transparent and overlaid on the false-color image in order to further suppress the visibility of the top painting, yielding the image displayed here. Image collection and processing by Dr. John Delaney, National Gallery of Art, Washington, D.C.
Areas in a painting that were painted with pigments containing heavy metals absorb more X-rays than areas painted with other pigments. Since the lighter passages in the underlying painting contain lead white, they show up especially well in X-radiography. This captures the brushwork in the face and the white shirt more effectively than infrared reflectography. Since Woman Ironing also contains lead white, the X-ray shows the brighter areas of the final composition prominently superimposed on the earlier painting.