Published in ScienceNOW, 2 Apr 2012
Possibly the only formal self-portrait of Leonardo da Vinci resides in the Royal Library of Turin, Italy. Some of its details are obscured, however, thanks to 500 years of paper yellowing. Scientists have long known that such yellowing can stem from cellulose—the main component of old, handmade paper—which oxidizes over time to develop colored molecular structures known as chromophores. Until now, however, researchers haven’t identified which chromophores are responsible. […]
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