A painted swatch of Cadmium yellow/red:
About the chemical structure:
| Chemical name: | Cadmium yellow: cadmium sulfide (CdS) Cadmium orange/red: cadmium sulfide (CdS) + cadmium selenide (CdSe) in varying proportion |
| Formula: | CdS (yellow); CdS + CdSe (orange/red) |
| Crystal system: | greenockite: Hexagonal - Dihexagonal Pyramidal (at Mineralogy Database) |
| Refractive index: | e=2.506, w=2.529 |
How can you identify Cadmium yellow/red?
Chemical identification:
The particle sizes of the deeper cadmiums are about fifty times larger than the paler varieties. They are transparent particles that appear in clusters, microscopically. Cadmium pigments are dissolved in hydrochloric acid and nitric acids and are unchanged by sodium sulfide
Usage and handling:
| Permanence: | Toxicity: |
|---|---|
| excellent. It does discolour however upon combined exposure to the light, water and CO2 forming cadmium carbonate. For that reason it can not be used in mural painting techniques. Pigment used on the damp wall will change. Pigment exposed to the same amount of light used on canvas or panel will not change. Cadmium pigments are classified as absolutely permanent with the exception that they are not suitable for the exterior applications and for mural painting techniques. also cadmium pigments tend to blacken when mixed with copper pigments. | MSDS (at Fisher Scientific) |
Literature:
Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1, L. Feller, Hrsg., Cambridge University Press, London 1986, p. 65 -108.
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