Introduction:
This lesson introduces copper’s role in artistic pigments, exploring historical and modern uses. Copper is found in ancient pigments such as malachite, azurite, and verdigris, and in contemporary pigments like phthalocyanine blue and green. The lesson focuses on using XRF (X-ray fluorescence) spectroscopy to identify copper in pigments, with particular emphasis on phthalocyanine blue, where copper is present in minimal amounts, requiring special adjustments to obtain an accurate signal.
Objectives:
- Learn to identify copper presence in various pigments using XRF spectroscopy.
- Gain proficiency in setting up XRF equipment to detect copper in low-concentration pigments.
Materials:
- XRF Spectrometer
- Pigments Checker STANDARD
Lesson Plan:
1. Introduction to Copper in Pigments:
- Discuss the historical use of copper in pigments and its importance in ancient art.
- Introduce modern copper-containing pigments, with an emphasis on phthalocyanine blue and green.
2. Setting Up XRF Spectroscopy for Copper Detection:
- Explain how copper has a strong XRF signal, but certain pigments with low copper content (e.g., phthalocyanine blue) require adjustments.
- Outline the adjustments in filter setup needed for low-concentration detection, focusing on low-energy peaks between 2-10 keV.
3. Practical Application: Identifying Copper in Pigments
- Sample 1: Malachite
- Position malachite sample for XRF acquisition.
- Analyze the spectrum, highlighting copper’s k-alpha and k-beta peaks at approximately 8 and 8.9 keV.
- Sample 2: Azurite
- Run XRF acquisition on azurite and compare the spectrum with malachite.
- Discuss differences in copper content, noting azurite’s higher copper count and resulting stronger signal.
- Sample 3: Phthalocyanine Blue
- Conduct an XRF acquisition on phthalocyanine blue, observing the low copper signal.
- Adjust filters to a 0.25 mm aluminum filter, increasing microampere settings, and examine the resulting spectrum for clearer copper peaks.
