CHEMISTS FOUND NEW PUZZLE IN THE WORKS OF DA VINCI

16.05.14

Known, perhaps, to everyone the painting by Leonardo da Vinci - Mona Lisa, a portrait of Gerard Donna Lisa, the wife of a silk merchant Francesco del Giocondo from Florence, written in 1503-1505, is at the same time the most enigmatic work of fine art of the Renaissance.
It is known that the current condition of the painting is bad enough, that is why the staff of the Louvre announced that they will no longer give its exhibitions. It is logical to assume that there required the measures for its restoration, strengthening layers of paint and prevent the formation of cracks, some of which, like the Louvre curators say, stay in a few millimeters above the head of the Mona Lisa.
In order to develop appropriate conservation techniques Louvre administration has decided to seek help from the chemists restorers and forensic chemists to determine the characteristics of noninvasive techniques and primer pigments used when da Vinci masterpiece was being written.

Red circle indicates the location pattern in which slow neutrons diffraction method enabled us to discover an unusual primer.
Researchers at the Jeffersonian Institute under the direction of Dr. Temperance V. Brennan decided to explore Renaissance painting using the diffraction of slow neutrons.

The difference between this method in comparison with X-ray diffraction and electron diffraction is that neutrons mostly interact with atomic nucleus and the magnetic moments of the electron shells of atoms.
This fact, first of all let us to determine the composition and structure of the studied object more precisely than RSA, and secondly - it has minimal chances of damage to the studied sample.
The study of the Mona Lisa by slow neutron has set the analyst, as, indeed, the specialists Heritage da Vinci, with another puzzle.

If the biggest part of the canvas of Mona Lisa consists of oil primer under the oil paints, which is  traditional for oil painting of the Renaissance and Baroque periods, then in a small area (in the upper right part of the picture, where you can guess the Ascension of the Sun) primer material appeared to be quite unusual for the XVI century. The analysis showed that in that place the basis of was canvas covered with carbon-chain oligomeric materials.

Repeated analysis of gained neutron diffractions showed that a small portion of fabric, consisting of no more than 15% of the area of the canvas, primered mostly with monodisperse oligomers performing block copolymers of vinyl chloride and styrene (up to now it was thought that the first samples of PVC were obtained accidentally in 1835 by Henri Victor Regnault).
It is also interesting that the found sample of block-copolymers has a very regular structure, the researchers gave it the name "regular block-copolymers". The feature of the structure is such that a certain amount of styrene structural units, which varies each time in the block, however, the block with this amount of units can be repeated in the structure of the oligomer several times, alternates with block consisting of 15 vinyl chloride structural units.

Counting the number of styrene structural units in the  block can encode any alphabetic characters, Brennan held computer analysis of such a "coded" information and made even more incredible assumption - deciphering the structure of oligomers by computer cryptalgorithm issued SMILES-formula mercazolilum - the material used to treat diffuse goiter, which is believed by some doctors, Lisa Gerard suffered by.

Neal Caffrey, a specialist in ancient cultural values, appreciates the analytical part of Brennan's work, but believes that the attempt to decipher the " polymer message" of da Vinci is farfetched . He says that if you use positional value system used in cultures, in which da Vinci is believed to have been an expert, it can be obtained a Latin phrase "Strati, et venit in pace" ( Earthlings, we come in peace ), if you use the Gaelic system - " two quarks for laird Clark "and other well-known enough now maxims.

As Caffrey believes copolymers were likely obtained randomly by da Vinci - we know that Master tended to experiment with paints and primers, because of which, such as the fresco "The Lord's Supper" has practically died. Caffrey adds that currently there are cases of detection of "modern" technological innovations in heritage objects - gold nanoparticles in the Cup of Lycurgus , carbon nanotubes in samples of Damascus steel , but it does not mean that the masters of antiquity received these materials, using the means available to us now informed scientific approach. In any case , the discovery is an important fact for biographers of da Vinci and professionals in saving its heritage. It is assumed that the work on non-invasive study of the materials used by Renaissance masters of the primers and paints, will be continued.

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