Edgar Collins regularly donated artwork to public museums all over the world. Th

Question

Edgar Collins regularly donated artwork to public museums all over the world. Through his travels, he has collected major and lesser-known works. He also developed a keen interest in finding undiscovered artwork. His current acquisition, a new Cézanne, was obtained from the infamous Josef Berg, who was known for passing counterfeits, and in 1995 a French curator had researched the lineage of all known works and concluded that no new paintings were likely. The painting is unsigned, but that is not unusual since Cézanne only signed a few of his paintings, and art historian, Dr. Philip Marden, has concluded that it is a previously unknown Cézanne.You work as a scientist at Spectrotech and have been assigned examine the painting and assess it’s authenticity. The company has done a few investigations previously for the museum and determined, using a combination of spectroscopic techniques, that a Rembrandt hanging in the Hague’s museum was painted by one of Rembrandt’s students. Describe the different spectroscopies you might use and how these would aide in revealing the authenticity of the painting.

Explanation / Answer

The authenticity of a painting can be verified by spectroscopic techniques such as UV-visible absorption spectroscopy, FTIR and Raman spectroscopy, X-ray fluoresecence (XRF) and Ultraviolet fluorescence spectroscopy. The strategy behind such characterization is to compare the pigments, binders and dyes in the given artwork with those used in an authentic artwork of Cezanne. We can also analyze whether the pigments and binders in the artwork under study were used during the period of the artist, Cezanne (19th century 1839-1906).

The principle and applicability of various spectroscopic techniques used to authenticate artwork are as follows.

UV-visible absorption spectroscopy:

In this technique, ultraviolet and visible radiation of wavelength ranging from 200 to 800 nm is incident on different regions of the paint and absorbance is measured as a function of wavelength. The absorbance is a measure of the brightness of the colour and indicates the age of the paint. A century old artwork will show low absorbance than a fresh artwork.

VIbrational spectroscopy

FTIR (Fourier Transformation Infrared) spectroscopy and Raman spectroscopy are vibrational spectroscopy techniques, complementary to each other. Both the techniques provide information about the type of binders and any charcoal backdrawing in the artwork. From the vibrational spectra, we can clearly find out the dyes and pigments used in the artwork. Certain dyes which are silent in FTIR (uses infrared radiation) spectroscopy, can be seen in Raman spectroscopy (uses visible light for characterization)

X-ray fluorescence and UV-fluorescence spectroscopy (both are luminescence techniques)

X-ray fluorescence (XRF) uses X-rays with high penetrating power to excite core electrons in metal ions present in the pigments. When the electrons relax, they emit characteristic x-rays. Thus XRF is used for elemental analysis of the paints present in the artwork. This information gives a good clue about the period of the artwork. For example, if the XRF spectrum of the artwork shows the presence of Titanium, Cadmium or Manganese, the artwork cannot belong to nineteenth century as pigments containing these metals were not in use during that period. Ultraviolet fluorescence spectroscopy provides information about the paint surface (about 25 micron thick layer) and indicates any effect of contamination.

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