It’s difficult for art conservators to restore damaged paintings and illustrations if they’re unsure exactly what’s caused the damage. Just as curing an illness without knowing its cause can become dangerous guesswork, art preservation projects that proceed blindly can risk ruining priceless works of art. Which is why, for decades, the restoration of Leonardo da Vinci’s presumed self-portrait from around 1510 has been stalled by researchers unsure where the damage came from.
The self-portrait, which depicts an elderly man drawn in chalk and is thought to represent Leonardo himself, has long been marred by reddish-brown spots. For years, researchers were unsure whether the spots—sometimes called “foxing spots”—were chemical or biological in origin. But now, a recent study published in Environmental Microbiology Reports claims that the spots were the result of several species of fungus, Discover reports.
According to the study, dust-borne iron particles likely damaged the paper long ago, disrupting its cellulosic structure and creating an opening for fungal organisms. Discover explains that different species of fungus likely burrowed into the already-damaged paper, ultimately creating the spots.
This discovery is big news for art conservators who can use their newfound knowledge to begin developing a restoration plan for the self-portrait. “Treatment strategies, however, are still far from perfect, but understanding the precise composition of the spots is an important pre-requisite for developing a conservation game plan,” Discover explains. “Once that is established, work will begin in a race against biology to keep da Vinci from fading further into the centuries-old paper.”