This lesson explores the use of zinc in coinage, highlighting both its advantages as a cheap metal and its limitations due to corrosion. Two case studies will be examined: the 20-cent zinc coin issued by the French Vichy government in 1941 and the modern U.S. penny.
Objectives
-
Understand why zinc was adopted for coinage in different historical contexts.
-
Recognize the corrosion problems of pure zinc coins, known as “zinc disease.”
-
Identify the composition of zinc-based coins through XRF spectroscopy.
-
Compare wartime coinage with modern strategies for cost-effective minting.
Materials
-
Vichy France 20-cent coin (1941)
-
U.S. pennies (post-1982 zinc core)
Lesson Plan
-
Introduce zinc as a low-cost but unstable material for coin production.
-
Present the Vichy coin as an example of pure zinc coinage, and discuss its surface degradation.
-
Examine the coin with XRF spectroscopy to confirm pure zinc composition.
-
Compare with U.S. pennies, explaining the shift from copper to zinc cores after 1982.
-
Demonstrate XRF spectra of coated and abraded pennies, highlighting differences in copper and zinc signals.
To reinforce the concepts discussed here, we also provide a video lesson that visually walks through the key points of this topic. Watching the video alongside the text can help you better understand and apply these ideas in practice.
The course XRF Spectroscopy for Art Examination introduces conservators, art historians, and scientists with interest in Art to the principles and practical applications of X-ray fluorescence (XRF) spectroscopy in the examination of artworks. The course starts with basic principles of XRF and gradually explores its role in identifying materials and methods used in the creation and conservation of art.
Course Objectives
- Understand the fundamentals of XRF spectroscopy and how it applies to the analysis of art.
- Learn the key features and limitations of XRF for examining art and archaeology.
- Gain skills in interpreting XRF spectra to identify specific elements in paint layers, inks and metals.
