Non-destructive testing methods cannot securely expose fake art
Analysis methods are only capable of clearly detecting fakes when non-contemporary materials are detected in artefacts. However, if the forgers have used substances whose contemporary use is described, for example, historical paper is used for printing and painting in the forgery of a book, materials science cannot provide evidence of a forgery.
This happened in the scientific investigation of the "star messenger", Sidéreus Nuncius, a 60-page study from 1610 with supposedly hand-painted Moon illustrations by Galileo Galilei. The volume emerged in 2005 in the New York antiquarian bookshop Martayan-Lan and was regarded as a sensation. Today the book is known to be a fake.
"Material analysis is only capable of unmasking a fraud when the forger makes use of materials which were used only after the date of origin of the supposed original," says Oliver Hahn, head of the Division of Arts and Cultural Analysis at the BAM Federal Institute for Materials Research and Testing and co-author of the third Galileo volume with the title: A GALILEO FORGERY. UNMASKING THE NEW YORK SIDEREUS NUNCIUS. In this third volume to be published on the 450th anniversary of Galileo Galilei (15 Feb.1564 - 29 Dec. 1641), the Galilei team of researchers, composed of experts from the fields of art, books, science, materials science and restoration history, correct their own results of the first two volumes.
Faced with the statement that this Sidéreus Nuncius copy is a fake, BAM have re-examined their data from previous studies and supplemented them with further tests on the paper and printer's ink. These tests were carried out according to previous measurement campaigns, with the requirement that no physical sampling was made. "We were of course aware when performing the measurements that non-destructive tests can provide less accurate findings than methods based on sampling. But the book was still considered unique and was supposed to remain untouched" says Hahn.
The New York Sidéreus Nuncius was not the only item tested by the BAM research team but also contemporary comparative pieces. The most important piece was the Sidéreus Nuncius of Graz, which is considered to be an authentic object. The researchers tested the chemical composition of the paper and the printer's ink using various non-destructive spectroscopic methods. The measurement results from the forgery (New York), and the original (Graz) showed none or only a slight difference, which makes the evaluation of authenticity very hard.
Although the X-ray fluorescence analysis of the printer's ink shows slight differences in the elemental composition, this is no proof that the printer's ink in the New York copy is a modern preparation. Both printer's inks are chiefly composed of organic materials. A non-destructive analysis of printer's ink, i.e. a substance composed of a binder and elemental carbon, is not sufficiently conclusive at the current state of science and technology.
Another opportunity to prove the authenticity of the volume is to determine the age of the paper and the printer's ink. The method of choice is the familiar C14 method. It is based on the fact that the three carbon isotopes 12C, 13C and 14C are bound in dead organic materials such as paper and printer's ink and the number of radioactive 14C atoms decreases according to the law of radioactive decay. The older the material, the lower the measured radioactivity. But even this method requires samples to be taken, which of course had to be avoided in the tests.
The investigation by the BAM Sidéreus Nuncius experts showed that the proof of authenticity of a cultural asset is not easy, especially if the counterfeiters have used contemporary materials.