On‐site Raman study of artwork: Procedure and illustrative examples

Abstract

Raman microspectroscopy conducted with transportable/mobile instruments allows for the non‐invasive identification of amorphous and crystalline phases of ancient masterpieces and outstanding artworks (objects, paintings and décor, building parts, etc.). Resonance Raman spectroscopy detects chromophore and dye traces. On the basis of examples (enamelled glass and pottery, enamelled metal, patinated/corroded metal, stained glass, sculptures, paintings, pastels, and drawings), this mini review discusses the main parameters (laser and optics choice, experimental procedure, etc.) and shows how phase identification contributes to a better understanding of innovant technology exchanges.

The Raman signature of protonic species as a potential tool for dating or authentication of glazed pottery

“…The absolute Raman intensity of the silicate signature was found to be an effective tool in the discrimination of similar types of glasses as a function of time according to their varying degrees of corrosion, which in turn affect the transparency of glass . The relative intensity of the Raman signature of protonic species incorporated in the glassy silicate network on the glass or glaze surface was also previously proposed as a potential tool for the discrimination of artefacts (kept in the same conditions) as a function of age . The results of our analyses on different types of glazed pottery samples showed that there is a correlation between the relative intensity of the broad Raman signature of the protonic species and the age of the artefact to a certain degree including the celadon or stoneware and porcelain samples.…”

“…A broad component is observed with submaxima at 2,700, 2,900, and 3,180 cm −1 . The broad bands at 2,700 and 2,900 cm −1 indicate the strongly H‐bonded species whereas the band at 3,180 cm −1 is assigned to the water molecules adsorbed at the glass surface or within the cracks . A weak broad band visible at 3,300 cm −1 also indicates the presence of water molecules in the sample whereas another weak narrow band at 3,730 cm −1 is assigned to the hydroxyl groups (Table and Figure b).…”

“…Figure S3 shows the as‐recorded and wave‐corrected Raman spectra of the Qing Famille Rose porcelain sample (Q‐r) obtained from preliminary measurements performed on the section of shards at different distances from the glaze surface in the high wavenumber region . Unfortunately, in this preliminary work, the selected wavenumber window (3,000–3,800 cm −1 ) being too small hinders the clear observation of all the components.…”

“…Raman microspectroscopy is now a well‐established technique for the characterization of covalently bonded compounds as those constituting ceramics and glass. Furthermore, mobile Raman set‐up allows the fast identification of crystalline and amorphous phases in a nonintrusive way on‐site and use of the technique has also developed rapidly for the authentication of glass, pottery, and enamelled objects . Raman spectroscopy is an optical technique, which is directly influenced by the optical properties of the materials analysed, such as transparency and colour.…”

“…The low intensity of the near infrared signature allows measuring the transmission through thick and optically clear (polished) samples (>mm). However, as a scattering technique, Raman spectroscopy requires no preparation of the sample . Preliminary measurements have pointed out the presence of protonic species signature in the Raman spectrum of ancient glazed pottery recorded at the very surface .…”