AIC's 43rd Annual Meeting

Despite extensive research into Pablo Picasso’s working methods and materials, as well as detailed analyses of a handful of his later paintings, comprehensive technical analysis of a work from his Blue Period has not been carried out. The Blue Room (1901, The Phillips Collection, Washington, DC) has been known since the 1990s to have another painting, a portrait, beneath its presentation surface. This presentation will describe results of a wide-ranging analysis of The Blue Room, including combined results from portable x-ray fluorescence (XRF), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy x-ray microanalysis (SEM-EDS), and synchrotron-radiation (SR) based XRF mapping of the entire painting. The goals of these measurements were to determine the elemental distribution of the combined paintings, and the feasibility of distinguishing features of the presentation surface and the hidden work. Numerous features of the buried portrait are identifiable in the XRF maps, which, along with hyperspectral imaging, are assisting in the ongoing interpretation of this painting. Cadmium carbonate (CdCO3) has been identified in the altered cadmium yellow (CdS) paints found Impressionist, early modernist, and post-Impressionist paintings. When it is concentrated at the surface of the paint layer, CdCO3 appears to be the result of the photo-alteration of CdS. However, in other cases CdCO3 is distributed throughout the thickness of the paint layer. CdCO3 is highly insoluble (Ksp of 1.0 ×10-12) and would not be expected to migrate from the painting’s surface. Plahter et al. have recently proposed that CdCO3 is present in cadmium yellow paints as residue from the indirect wet process synthesis of CdS using CdCO3 and Na2S.[1] To determine the role of CdCO3, as well as cadmium oxalates and sulfates, microspectroscopy and microdiffraction of altered and unaltered cadmium yellow samples from Henri Matisse’s 1906 Flower Study (The Barnes Foundation, Philadelphia, PA) were carried out. X-ray fluorescence mode allowed precise mapping of elemental distribution, and Full Field X-ray Near-Edge Absorption Structure (FF-XANES) allowed mapping the chemical speciation of cadmium and sulfur. The XANES data support Plahter’s hypothesis for the 1906 still life. Yellow orpiment (As2S3) and red-orange realgar (As4S4) are arsenic sulfides that have been used as pigments since antiquity. Orpiment becomes paler and colourless upon exposure to light, while realgar turns bright yellow. A photo-oxidation process involves the conversion of orpiment to colorless arsenic trioxide (arsenolite, As2O3) and realgar is altered to pararealgar (As4S4, an isomer of realgar), and then eventually to arsenic trioxide. Here, we also report on this transformation and characterization of the reaction products, based on investigation of two very different works of art from early 18th century: Still life with five apricots by the Dutch master Adriaen Coorte (1704) (Royal Picture Gallery Mauritshuis, The Hague, The Netherlands) and an early American polychromed chest on stand attributed to Charles Guillam painted in Saybrook, Connecticut between 1710-1727 (Winterthur Museum, Winterthur, USA). The µXANES identification of further degradation products of realgar will be presented, in addition to their subsequent mobility in different paint systems. 1. Plahter, U. and B. Topalova-Casadiego. Cadmium Yellow in "The Scream" painted by Edward Munch. in The National Gallery Technical Bulletin 30th Anniversary Conference. 2011. London: Archetype.