- How kind it was of Monsieur Van Gogh - to sign only with his name! For me, this is a time saver.
Papa Bonnet forging Van Gogh's signature. Comedy film "How to steal a million"
Historical science technologies. Probably, there is no person in our country who has not seen this American comedy directed by William Wyler with the inimitable Audrey Hepburn and charming Peter O'Toole in the lead roles. It is about the abduction from the museum of the marble statuette of Venus Cellini (the creation of Benvenuto Cellini), which was actually made by Bonnet's father from his grandmother, and, of course, even before she began to overeat at dinner. The intrigue revolves around the expert Dr. Bauer, who must authenticate Venus, the insurance for which is exactly one million dollars. And Bonnet's daughter, Nicole, explains to her dad that forgeries in sculpture do not work out, because there is such a thing as potassium-argon, with which they determine the age of the stone, the place where it was mined, and even the address of the sculptor who is the product sculpted. Then love intervenes and a lot of interesting things happen. However, this is a movie. And cinema is cinema! But how, in reality, modern scientists determine whether this or that marble artifact is genuine, or is it nothing more than a well-made fake? This is what our story will go on today, and in order for it not to be too academic and boring, it will be illustrated by shots from the movie "How to Steal a Million" and photographs of kuros from the most famous museums in the world.
As an example of such work, we will take a real case that occurred back in 1984. One could find more modern examples, but here it is important to show how this was done even then. Because today science has gone even further.
That year, the J. Paul Getty Museum in Malibu, California, was offered an antique marble statue of a youth athlete (kouros). The statue was more than two meters high and is perfectly preserved, despite the fact that it was more than 2500 years old. The problem arose due to the fact that art critics did not know it, as it was in one of the private collections in Sweden. The newspapers got to the bottom of the fact that for the kuros his owner requested from 8 to 12 million dollars, that is, an exceptionally large amount for a completely unknown statue.
Marion Tru, curator of the museum of the department of antiquities, invited art critics to see it, and most of them considered it to be genuine. But there were those who doubted its authenticity, motivating their opinion by the fact that the statue has stylistic deviations from all known samples. And something really well preserved! Then she was examined in ultraviolet rays, which made it possible to find more suspicious features. Usually, ancient marble products in ultraviolet light have an amber hue with some purple blotches. While this figure had a light purple hue, it is usually characteristic of modern pieces. Naturally, no one was going to pay millions for a fake, so the workers turned to scientists.
Stanley V. Margolis was invited, who has been doing research for over a year. Moreover, he was even allowed to drill a core from the statue in order to take small samples of stone for analysis. Until then, none of the marble sculptures had been subjected to such a scrupulous scientific analysis, but today such scientific methods of identifying the authenticity of marble sculptures are used in all major museums in the world.
Prior to this, experts studied the style of the sculpture and used the method of comparative iconography to distinguish the fake artifact from the original. Well, the age of the sculpture was judged by its surface layer, the so-called patina. Moreover, marble turned out to be very resistant to weathering, so that traces of aging and the effects of the environment on it with the naked eye are impossible. However, the demand for "antiques" over time led to the fact that fake sculptures began to be buried in the pasture where cows were grazing, and also to specially age their surfaces with acid vapors.
At the same time, geochemists have a wealth of experience in studying the properties of marble and such rocks as limestone, which, as you know, under the influence of high temperatures and pressures, turns into marble. Thanks to the study of rocks extracted by drilling from the bottom of the ocean, it was possible to date the ice ages, and much to learn for the reconstruction of those natural conditions under which, for example, the extinction of dinosaurs occurred on our planet.
There are many types of analyzes that allow you to "talk" even the most "silent" stone. For example, the ratios of stable isotopes of carbon and oxygen in marble and limestone samples have been found to vary depending on their origin. Isotope analysis makes it possible to identify changes caused by weathering or burial in the soil. Microscopic analysis of a piece of marble in polarized light reveals inhomogeneities in its structure, and by measuring the wavelength of X-rays emitted by samples during irradiation, one can easily determine even the smallest concentrations of impurity elements in them. That is why, by the way, after 1945 it became extremely problematic to use stone from quarries for forgery, as well as wood and paper … Since then, a lot of all radioactive rubbish has got into the atmosphere, and it is very easy to fix all these man-made elements.
The Kuros in question was carved from dolomite, a highly resistant type of marble, circa 540 and 520. BC NS. The statue itself consisted of seven parts and had a height of 206 cm.
With the permission of the owner, they drilled a column with a diameter of 1 cm and a length of 2 cm below the right knee, where a small crack had formed in ancient times. The column was cut into thin layers and they began to examine them through an electron microscope. Other samples were taken using a mass spectrometer. X-ray diffraction and fluorescence methods were also used to determine the content of impurities and foreign inclusions in them.
First of all, it turned out that the marble from which the kouros was made is practically pure dolomite (or calcium-magnesium carbonate), that is, a rarer variety of marble than marble, which consists of calcite (calcium carbonate). It is both more durable and resistant to weathering, as a result of which this statue, apparently, is so well preserved.
By chemical composition, it was possible to find the place where this marble was mined: the ancient quarries at Cape Vafi on the island of Thasos, the oldest among those where dolomite marble was mined from time immemorial. Well, historians, as it turned out, knew that it was on the island of Thasos that the production of large kouros was located. That's just the question of authenticity, this did not solve, because marble on this very island is mined to this day.
Then the surface of the statue was examined with a strong optical microscope and it was found that it was covered with a thin layer of brown patina, consisting of iron oxides, clay-soil minerals and even inclusions of manganese oxides. In addition, the most weathered surface of the kuros was covered with calcite 10-50 µm thick. The research was carried out at the University of California, but later replicated at the Institute for the Conservation of Cultural Monuments at Marina del Rey in Los Angeles.
And this was the main argument in the question of the antiquity of the statue. Even in a modern laboratory, turning dolomite particles into calcite on the surface of a two-meter statue is completely unthinkable. In addition, such elements as strontium, manganese, etc. would have been found in the "fresh" dolomite and calcite layer. And they were in the calcite layer, but completely absent in the dolomite layer! That is, it was proven that the calcite layer on the statue was formed naturally.
Based on these data, scientists concluded that the calcite layer on the museum of interest to the kouros was the result of weathering, to which the statue was subjected for many, many centuries.
However, the staff of the Getty Museum found all this a little and they made a detailed comparison of the statue with 200 other statues of the kouros that have come down to us in whole or in part, and it also confirmed its antiquity. So, after 14 months of painstaking research, the authenticity of the kouros was proven. The museum has finally decided to buy it. Already in the fall of 1986, it was exhibited in a museum, and it was protected from tremors by a complex system of cables and springs made, moreover, of stainless steel.
Well, today, for the successful analysis of antique marble sculptures, just a pinhead sample taken from a place on the sculpture where the most sophisticated connoisseur of this "withdrawal" will not even notice is enough.
References:
Stanley W. Margolis. Authentication of antique marble sculptures using geochemical methods. Scientific American. Edition in Russian. 1989. No. 8. S. 66-73.
