The following caused black spots on Leonardo da Vinci’s Codex Atlanticus

Researchers at the Politecnico di Milano in Italy examined mysterious black spots on a folio by Leonardo da Vinci Codex Atlanticus and confirmed the presence of starch and vinyl adhesives in the affected areas. According to a recent article in Scientific Reports magazine, the adhesives were most likely applied during a previous restoration some 50 years ago. They also identified a likely cause of the dark spots: nanoparticles of a mercury sulfide called metacinnabar in the protective paper holding the folio, though it’s unclear how this unusual black crystalline phase might have formed.

Da Vinci produced more than 13,000 pages in his notebooks (later compiled into codices), less than a third of which have survived. The notebooks contain all sorts of inventions that anticipate future technologies: flying machines, bicycles, cranes, rockets, machine guns, an “unsinkable” double-hulled ship, dredgers for clearing harbors and canals, and floating shoes resembling snowshoes to empower a human on to go to the water. The notebooks also contain detailed notes by da Vinci on his extensive anatomical studies. Most notably, his drawings and descriptions of the human heart showed how heart valves could slow blood flow, 150 years before William Harvey worked out the basics of the human circulatory system.

The largest single movement is the 12-volume Codex Atlanticus, in which (among other observations) da Vinci foresaw the possibility of building a telescope when he wrote of “making glasses to see the moon magnified” – a century before the invention of the instrument. The codex underwent an extensive 10-year restoration from 1962 to 1972, during which each individual folio in the 12 volumes was framed by a “passepartout”: a protective paper sleeve consisting of three modern layers of paper glued to each folio with it they can be handled and displayed more easily. It also allowed reading and checking the double-sided documents. The codex is currently in the Biblioteca Ambrosia in Milan.

In April 2006, a representative at the Metropolitan Museum of Art in New York City was alarmed to discover what appeared to be red, black, and purple mold invading the museum Codex Atlanticusand the swelling of some pages – despite the fact that the Code has been kept in a carefully controlled microenvironment since 1997. A conservation institute in Florence, Italy, immediately launched an investigation.

The concern was justified. Studying the microbial species that accumulate on artworks may lead to new ways to slow the deterioration of priceless aging artworks. In fact, in 2020, scientists analyzed the microbes found on seven of da Vinci’s drawings. Researchers at the University of Natural Resources and Life Sciences in Vienna, Austria, used a third-generation sequencing method called Nanopore, which uses protein nanopores embedded in a polymer membrane for sequencing, and combined Nanopore sequencing with a whole genome amplification protocol.

They found that each drawing had its own unique microbiome. But they were surprised to find that overall, bacteria dominated the fungi in the microbiomes of the drawings, contradicting the widely held belief that fungi would be more dominant due to their higher potential to colonize paper-based works. Many of these bacteria are typically found in human microbiomes, suggesting they got onto the drawings during the restoration – although one could speculate whether they came from the artist himself. (The Austro-Italian team was unable to definitively determine whether any of the microbial contaminants date back to da Vinci’s time.) Other bacteria were typical of insect microbiomes and may have been introduced long ago by flies depositing excrement on the drawings.