Improved Tomography Sees Through Art

Museum conservators often want to visualize layers of varnish and paint on artwork, for example, when they need to replace varnish on an old masterpiece during restoration. A research team based in England has now improved a technique called ultrahigh-resolution Fourier domain optical coherence tomography so that it can see through a painting’s layers noninvasively—and with the same depth resolution (around 1 μm) as traditional but destructive sampling methods (Opt. Express 2015, DOI: 10.1364/oe.23.010145). This improved tool for cultural heritage science comes courtesy of researchers developing tomography for visualizing tissue layers in the eye, notes the team, led by Haida Liang of Nottingham Trent University. Liang and her team needed to modify the eye technology to not lose sensitivity in deep paint layers. Then they demonstrated the technique’s strengths by visualizing the varnish and paint layers of “The Madonna and Child,” a painting from before 1600, perhaps by Raphael, at the National Gallery in London. The team compared the new method with a variety of other analysis techniques. The painting’s varnish is so yellowed that part of the Madonna’s dress now appears green instead of blue.