Verdigris comprises various copper acetates produced by exposing copper plates to acetic acid vapors from vinegar or fermenting grape pomace in the stack process. Known since antiquity and described by Theophilus and Cennini as viride Graecum or verderame. Widely used in medieval manuscripts and panel painting through the 17th century. Chemically unstable, sensitive to moisture and sulfur compounds, often causing darkening or complete loss of color over time. Reacts with many pigments including lead whites and sulfur-containing colors. Its instability and toxicity led to replacement by more stable synthetic greens in the 18th-19th centuries. Often converted to copper resinate for oil glazing.
Usage Timeline:
| Pigment | Prehistory <3000 BCE | Antiquity 3000 BCE–500 CE | Medieval 500–1400 CE | Early Modern 1400–1800 CE | Industrial 1800–1950 CE | Present 1950–today |
|---|---|---|---|---|---|---|
| Verdigris |
Key Properties:
| Properties: | Blue-green crystalline appearance; Semi-transparent to transparent; Chemically unstable |
| Usage: | Antiquity to 19th century |
| Source: | Artificial/Alchemical |
| Toxicity: | Moderate to high toxicity (copper salts) |
| Fresco: | No |
| Tempera: | Yes |
| Oil: | Yes (unstable) |
| Chemical description: | Basic copper acetate, Cu(CH₃COO)₂·Cu(OH)₂·5H₂O |
| Visualization: | Visible microscopy, often degraded to brown |
| Identification: | XRF (Cu), Raman, FTIR, SEM-EDS |