➞ DIFFERENT WAVELENGTHS In addition to UV fluorescence, there are more ways to see paintings with light outside of the visible spectrum.
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INFRARED LAYER CAKE Photographing a painting in detail with an infrared camera – which picks up light with waves longer and redder than red – can reveal brushstrokes well beneath a painting’s top layer. That’s how investigators confirmed the existence five years ago of a hidden work by Pablo Picasso underneath The Blue Room (1901).
Deliberately showing their tracks, restorers select paints that can be detected under ultraviolet light and easily removed, if desired, to restore the painting to a prior state. Under the UV lamp, this lightcolored paint reflects dark brown.
A layer of white underpaint probably was part of the original work. Restorers appear to have added their own lead white paint to areas of wrinkle damage to mend cracks and promote the adhesion of more layers. The metal in the paint fluoresces violet.
X-RAY COLOR VISION Pigments in paint contain metals such as iron, lead and zinc that absorb X-rays, making this kind of very-short-wavelength imaging useful for seeing mixtures of colors more precisely than the eye. The technique could provide data to compare different paintings by the same artist or to identify a forgery.
APRIL 2019
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