From lapis lazuli to ultramarine blue: investigating Cennino Cennini’s recipe using sulfur K-edge XANES

Journal Article · Fri Sep 22 00:00:00 EDT 2017 · Pure and Applied Chemistry

DOI:https://doi.org/10.1515/pac-2017-0502· OSTI ID:1437447

Ganio, Monica ^[1]; Pouyet, Emeline S. ^[2]; Webb, Samuel M. ^[3]; Schmidt Patterson, Catherine M. ^[1]; Walton, Marc S. ^[2]

---

1. The Getty Conservation Institute, Los Angeles, CA (United States)
2. Northwestern Univ., Evanston, IL (United States)
3. SLAC National Accelerator Lab., Menlo Park, CA (United States)

As one of the most desired and expensive artists’ materials throughout history, there has long been interest in studying natural lapis lazuli. The traditional method of extracting the blue component, lazurite, from lapis lazuli, as outlined in Cennini’s Il Libro dell’Arte, involves a lengthy purification process: (1) finely grind the rock; (2) mix with pine rosin, gum mastic, and beeswax; (3) massage in water to collect the lazurite. Repeating the process produces several grades of the pigment, typically referred to as ultramarine blue. Here, we investigate the sulfur environment within the aluminosilicate framework of lazurite during its extraction from lapis lazuli. The sulfur XANES fingerprint from samples taken at the different stages in Cennini’s extraction method were examined. All spectra contain a strong absorption peak at 2483 eV, attributable to sulfate present in the lazurite structure. However, intensity variations appear in the broad envelope of peaks between 2470 and 2475 eV and the pre-peak at 2469.1 eV, indicating a variation in the content of trisulfur (S₃^–˙) radicals. By studying the effect of each step of Cennini’s process, this study elucidates the changes occurring during the extraction and the variability within different grades of the precious coloring material. The increasing application of XANES to the study of artist’s materials and works of art motivated extending the research to assess the possibility of X-ray induced damage. Direct comparison of micro-focused and unfocused beam experiments suggests an increase of the S₃^–˙ radicals with prolonged exposure. Furthermore, analysis indicates that induced damage follows first-order kinetics, providing a first assessment on the acceptable amount of radiation exposure to define the optimal acquisition parameters to allow safe analyses of lapis lazuli and ultramarine pigments.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1437447
• Journal Information: Pure and Applied Chemistry, Vol. 90, Issue 3; ISSN 0033-4545
• Publisher: IUPAC
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Cennino Cennini
ChemCultHerit
lapis lazuli
radiation damage
ultramarine
XANES