This lesson explores the role of cobalt (element 27) in the history of pigments and its analysis using XRF spectroscopy. Cobalt’s significance spans centuries, from its use in early smalt pigment to its contribution to modern cobalt-based pigments. Through this lesson, participants will gain insight into the XRF spectral characteristics of cobalt and its compounds, and how these properties aid in pigment identification.
Objectives
- Understand the historical importance of cobalt in art and its role in pigment production.
- Analyze the XRF spectral features of cobalt and its various compounds.
Materials
- Reference samples of cobalt-based pigments in Pigments Checker STANDARD (e.g., smalt, cobalt blue, cobalt cerulean blue).
- XRF spectroscopy equipment with Routine filter setup.
Lesson Plan
Introduction to Cobalt in Art
- Discuss the historical use of cobalt, beginning with smalt in the 15th century.
- Highlight the development of cobalt-based pigments in the 19th century, including cobalt blue, cobalt cerulean blue, cobalt chromite blue, and others.
- Explain the enduring relevance of cobalt pigments in modern art.
XRF Spectral Characteristics of Cobalt
- Introduce the key XRF lines for cobalt: Kα at 6.9 keV and Kβ at 7.7 keV.
- Explain the impact of different XRF filter setups (low-keV vs. routine) on signal strength and spectrum clarity.
Analysis of Cobalt-Based Pigments
- Examine the XRF spectra of smalt, demonstrating strong signals using low-keV filters and acceptable detection with routine filters.
- Discuss the varying XRF signals of other cobalt-based pigments, from cobalt violet (strongest signal) to cobalt cerulean blue (weakest signal).
