An on-site Raman and pXRF study of Joseph Coteau and Philippe Parpette’s jewelled porcelain: a summit of ceramic art

Abstract

Highlights:-Non-invasive mobile approach to characterise artist materials implemented in Modern paintings -Validation of Specular Reflectance Infrared Spectroscopy analyses to identify paint binders -Combination of Raman and infrared spectroscopy for identifying Modern paints binders and pigments -Contactless spectroscopic identification of the binders and pigments of polymeric paints -On-site analytical study of artworks by German and Italian painters of the 1960s Abstract . Seven artworks representing the diversity of paints used around the 1960s and created by German and Italian painters (J. Albers, A. Bonalumi, L. Boille, T. Scialoja and M. Schifano) were studied onsite at the Galleria Nazionale d'Arte Moderna (Rome) with mobile instruments. We present a methodology based on Specular Reflectance Infrared Spectroscopy (SR-FTIR) adapted to unvarnished paintings. Complementary measurements have been performed by Raman spectroscopy. Characteristic bands regarding as-recorded infrared reflectance spectra and Kramers-Kronig Transformationconverted absorbance spectra are identified according to literature and reference spectra recorded on representative commercially available paints. To distinguish the different binders by SR-FTIR, wepropose spectroscopic markers as the comparison of the intensity of carbonyl band around 1730-1735 cm -1 with bands at ~1160 (for acrylic), ~1230 (for PVAc), and 1270 cm -1 (for alkyds). On the other hand, oil/resin binders are characterized by intense and thin CH 2 , CH 3 IR absorption bands around 2920-2850 cm -1 , combined with an intense 1260 cm -1 band and a characteristic concave cradle shape (between ca. 1750 and 1260 cm -1 ). The results obtained establish the relevance of the implemented mobile non-invasive infrared spectroscopy analytical approach by successfully identifying acrylic, vinylic, oil media and enamel paints, with or without opacifiers, which is supplemented by Raman analyses for pigment identification.

High‐fired early English porcelains of the ‘A’‐marked group, east London (c. 1744): A Raman spectroscopy and electron microscopy compositional study

“…Pigments applied to English porcelain from a related period have previously been discussed. [ 24,49,50,72–74,76 ]…”

“…The higher the lead oxide concentration, the higher the depolymerisation will be, lowering the melting point and hence the intensity of the 996 cm −1 band. Colomban et al [ 50 ] reported that lead‐rich enamels exhibit a strong stretching band at 980 cm −1 and alkali‐lead enamels which are less depolymerised and therefore have less flux, are fired at a higher temperature and are characterised by a band at ~1000–1010 cm −1 . And enamels with strong components at 1048 and 1050 cm −1 are characteristic of an alkaline‐rich glass.…”

“…Thus, different firing temperatures are required for the enamelling of metal and porcelain. [50,72] However, these various authors noted that there are similarities between metal enamels and pottery glazes, particularly the enamel compositions and the pigments selected for decoration. Fired gilding on porcelain was conducted at the end of the 17th century to the early 18th century at the Saint-Cloud factory, and gold foils started to be enamelled there for the first time.…”

“…Pigments applied to English porcelain from a related period have previously been discussed. [24,49,50,[72][73][74]76] Ordered carbon, diamond and graphite have sharp peaks at 1331 and 1581 cm À1 related to sp 3 and sp 2 hybridisation of the carbon bands. Thus, the broad bands of amorphous carbon at $1300 cm À1 may be assigned to diamond-like vibration involving C sp3 -C sp2 bonds and to a graphite-like band at $1600 cm À1 involving C sp2 bonds.…”

“…And, in instances, the known, deliberate addition of arsenic into some formulae was practiced. [50,81] It is likely that the mined ore would contain traces of other transition elements including Mn, Fe, Ni and Cr, all of which are potentially able to modify the shade of blue obtained. The smalt, which is incorporated into a potassium-rich glass, has been incorporated into a lead glaze to produce the enamel applied to Cup 1.…”