This lesson explores the role of bromine in modern and contemporary pigments, focusing on its chemical properties, applications in modifying pigments, and its detection in artistic materials. We will examine eosin as a case study and analyze its XRF spectrum.
Objectives:
- Understand the role of bromine in modifying organic pigments, particularly azo pigments.
- Identify the presence and behavior of bromine in pigments using XRF spectroscopy.
- Explore eosin as an example of bromine-containing pigments and its use in modern art.
Materials:
- Pigments Checker – Modern and Contemporary Art Version (including eosin sample).
- Potassium bromide (KBr) sample for XRF analysis.
- XRF spectrometer with routine filter setup.
Lesson Plan:
- Introduction to Bromine in Pigments: Discuss the chemical role of bromine in modifying organic pigments, emphasizing its impact on color and lightfastness. Highlight the substitution of hydrogen with bromine in large organic molecules to enhance pigment properties.
- Case Study: Eosin: Introduce eosin as a bromine-containing dye. Discuss its historical use by Vincent Van Gogh in his later works and the associated challenges, such as lightfastness and degradation.
- XRF Analysis of Bromine:
- Present the characteristic X-ray lines of bromine (Kα 11.9 keV, Kβ 13.3 keV).
- Demonstrate the use of potassium bromide as a baseline for bromine detection.
- Analyze the XRF spectrum of the eosin sample from the Pigments Checker, noting the diluted bromine signal.
