Conserving a Leonardo da Vinci painting

Updated 1219 GMT (2019 HKT) November 10, 2011
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Dianne Dwyer Modestini, who conserved the "Salvator Mundi," at work in her studio. CNN
The restoration work to the "Salvator Mundi" involed cleaning off layers of varnish and over-paint, repairing a crack in the wood panel and re-touching damaged areas of the painting. Copyright 2011 Salvator Mundi, LLC/ Photo Tim Nighswander/Imaging4Art
"The Virgin of the Rocks," at the National Gallery, after an 18-month conservation treatment. Copyright The National Gallery, London