This lesson explores the role of sulfur in the analysis of pigments. Sulfur is key to understanding pigments like vermilion, gypsum, and ultramarine. The lesson highlights sulfur’s spectral characteristics, its detectability in different materials, and its significance in pigment identification.
Objectives
- Understand the role of sulfur in pigments.
- Identify the sulfur K-alpha and K-beta lines and their corresponding energy levels.
- Analyze and interpret XRF spectra of sulfur-containing materials, including sulfur minerals, vermilion, gypsum, and ultramarine.
Materials
- Collection of materials for testing:
- Sulfur mineral sample.
- Vermilion (Pigments Checker).
- Gypsum (Pigments Checker).
- Artificial ultramarine (Pigments Checker).
Lesson Plan
1. Introduction to Sulfur in Pigments
- Discuss the importance of sulfur in pigments analysis and its presence in ultramarine, vermilion, and gypsum.
- Use the transmission calculator to demonstrate the feasibility of detecting sulfur at low energies.
- Input parameters: air (10 mm thickness) and X-ray energy (2.3 keV).
- Analyze the transmission result (65%) and its implications for sulfur detection.
3. Analysis of Sulfur in Different Materials
- Sulfur Mineral Sample
- Test the sulfur mineral and observe the spectrum.
- Discuss the strong sulfur peak at 2.3 keV and the high count rate (190,000 counts).
- Compare with aluminum (20000 counts) to highlight sulfur’s detectability.
- Vermilion (Artificial)
- Test vermilion, focusing on its composition (mercury sulfide: HgS).
- Identify overlapping spectral lines (mercury M-line and sulfur K-line).
- Discuss how XRF can detect sulfur content in addition to mercury.
- Gypsum
- Test gypsum (hydrated calcium sulfate) and analyze its spectrum.
- Note similarities in sulfur intensity compared to vermilion.
- Ultramarine (Artificial)
- Test ultramarine pigment and examine sulfur peaks.
- Compare sulfur intensity with vermilion and gypsum, noting the lower count (20000).
- Discuss the structure of ultramarine as a silicate lattice with aluminum and sulfur components.
