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Rare compound detected in the ‘Mona Lisa’ reveals a new secret, study says
Leonardo da Vinci was a painter, inventor and anatomist, to name just a few of his talents — and now, you can add innovative chemist to the polymath’s many gifts. It turns out the master artist was more experimental with his renowned “Mona Lisa” than previously thought — and was likely the creator of a technique seen in works created a century later, a new study suggests.
By using X-ray diffraction and infrared spectroscopy, a team of scientists in France and Britain has detected a rare mineral compound within the iconic piece. The finding provides fresh insight into how the work from the early 1500s was painted, according to the study recently published in the Journal of the American Chemical Society.
Along with lead white pigment and oil, the compound — known as plumbonacrite — was found in the base layer of the paint. A study published in 2019 had identified the mineral in several 17th-century works by Rembrandt, but researchers had not come across it in works from the Italian Renaissance until the new analysis.
Plumbonacrite forms when lead oxides combine with oil. Mixing these two substances on a palette is a technique that later artists like Rembrandt used to help the paint dry, according to the study. Detecting the rare compound in the “Mona Lisa” suggested that Leonardo could have been the original precursor of this approach, said Gilles Wallez, an author of the latest study and a professor at Sorbonne University in Paris who also was a coauthor on the 2019 report.
“Everything which comes from Leonardo is very interesting, because he was an artist, of course, but he was also a chemist, a physicist — he had lots of ideas, and he was an experimenter … attempting to improve the knowledge of his time,” Wallez said.
“Each time you discover something on his processes, you discovered that he was clearly ahead of his time,” he said.
The “Mona Lisa,” like many other paintings from the 16th century, was created on a wood panel that required a thick base layer, Wallez said. The researchers believe that Leonardo had made his mixture of lead oxide powder with linseed oil to produce the thick coat of paint needed for the first layer, while unknowingly creating the rare compound.
Analyzing the ‘Mona Lisa’
Nowadays, researchers aren’t allowed to take samples from the masterpiece, which resides at the Louvre in Paris and is protected behind glass, Wallez said. Using a 2007 microsample that had been taken from an area of the artwork just behind the frame, however, scientists were able to analyze the paint by using a high-tech machine called a synchrotron. The particle accelerator allowed the team to study the speck’s composition on a molecular level.
“These samples have a very high cultural value,” Wallez said. “You can’t afford to take big samples on a painting, so a synchrotron is the best way to analyze them.”
The base layer of Leonardo’s mural “The Last Supper” was also found to have the same chemical makeup as the “Mona Lisa” even though the mural was painted on a wall, according to the study. The scientists had a much wider scope of samples from “The Last Supper” to look at, 17 in total, which came from the paint flaking off the wall over time, Wallez said.
The “Mona Lisa” and “The Last Supper” are two out of fewer than 20 known paintings Leonardo made in his lifetime. Researchers hope they can discover more about the artist and his works with time.
“We have long known that Leonardo was an inveterate experimenter,” said William Wallace, a distinguished professor and chair of art history and architecture at Washington University in St. Louis.
“Therefore, it is not all surprising that we see him experimenting in other media, especially given his dedicated search for the best painterly techniques (often untraditional) to create his ‘living’ works of art,” said Wallace, an expert in Renaissance art and architecture who was not involved in the study.
注释：
anatomist: n
表示" 解剖学家"，means "an expert in anatomy"，如：Davidson Black is the anatomist and anthropologist of Canada.步达生是加拿大解剖学家与人类学家。
polymath: n; adj
表示"博学的人;知识广博的"，means "a person of great and varied learning"，如：Susan, pressed to define the word “polymath,“ was both sweet and solemn. 苏珊不甘示弱,说“博学者”是可爱的也是严肃的。
diffraction: n
表示" [物理]衍射；绕射"，means "when light passes sharp edges or goes through narrow slits the rays are deflected and produce fringes of light and dark bands"，如：Another important wave phenomenon is diffraction. 另一个重要的波现象是衍射。
spectroscopy: n
表示" [物]光谱学"，means "the use of spectroscopes to analyze spectra"，如：The parity of atomic states is important in spectroscopy. 原子状态的宇称性质在光谱中是重要的。
pigment: n
表示"色素； 颜料"，means "dry coloring material (especially a powder to be mixed with a liquid to produce paint, etc.)"，如：This pigment is a good common food additive. 该色素是稳定性好的食品添加剂。
plumbonacrite: n
表示"水白铅矿"，
Rembrandt: n
表示"伦伯朗(van Rijn [Ryn]；1609-1669；荷兰画家)"
Italian Renaissance: n
表示"文艺复兴"，means "the early period when Italy was the center of the Renaissance"，如：He was a child of the Renaissance. 他是文艺复兴时期的产物。
precursor: n
表示" 先驱；前任；前兆"，means "something that precedes and indicates the approach of something or someone"，如：Opposition by colonists to unfair taxation by the British was a precursor of the Revolution. 殖民地居民对英国不公正税收的反抗预示着革命的到来。
linseed: n
表示"亚麻籽"，means "the seed of flax used as a source of oil"，如：Is linseed oil edible?亚麻籽油可以食用吗？
synchrotron: n
表示" 同步加速器；同步回旋加速器"，如：The Synchrotron has also played an important part in advances in air safety. 同样,同步加速器在先进的航空安全性方面发挥着重要的作用。
mural: n
表示" 壁画"，means "a painting that is applied to a wall surface"，如：There is a large mural in the temple. 那个寺院里有一幅很大的壁画。
inveterate: adj
表示" 根深蒂固的；成瘾的"，means "habitual"，如：It seems that your inveterate prejudice utterly affected your judgement. 看来你根深蒂固的偏见已经完全影响了你的判断力。
中文简要说明：
意大利16世纪画家达文西的作品《蒙娜莉萨》（Mona Lisa）堪称全世界最知名的画作，凭着一抹神秘的微笑，每年吸引成千上万游客造访法国罗浮宫。最近科学家在画上发现一种特殊涂层，能加速画作干燥，过去从未出现在同时代的画作中，显示达文西可能领先同业，发明出先进的化学技术。
据CNN报导，这项研究由英国和法国科学家合作，透过X光绕射和红外线光谱术，在《蒙娜莉萨》画作底层检测到一种水白铅矿（plumbonacrite）的化合物。这种物质由氧化铅和油混合而成，涂在木质画板上当作底层，能加速作品干燥。过去曾在17世纪画家林布兰（Rembrandt van Rijn）的作品中出现，却是首次现身在16世纪画作中。
主导研究的法国索邦大学（Sorbonne University）教授瓦莱兹（Gilles Wallez）认为，达文西（Leonardo da Vinci）很可能无意中混和物质，因此发现了水白铅矿，成为这项技术的先驱：「达文西是画家，但他同时也是一位化学家和物理学家，透过实验来实现脑中的诸多构想。」
这个重大发现得来不易，因为科学家无法直接检测名画《蒙娜莉萨》，只能利用2007年从画上一角取得的微量样本，利用同步加速器（synchrotron）检视其中的分子组成。除了《蒙娜莉萨》之外，达文西另一件名作《最后的晚餐》也运用了水白铅矿技术。
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