Red ochre consists of natural clays containing hematite (iron oxide) and varying amounts of silica, alumina, and other minerals. One of humanity’s oldest pigments, used in prehistoric cave paintings at Lascaux and Altamira. Prepared by mining ocherous earths, grinding, and washing to remove coarse particles. Burnt ochre is produced by calcining yellow ochre at 250-400°C, converting goethite to hematite. Regional varieties include Sinopia, Venetian red, Pozzuoli red, English red, and burnt ochres, differing in hue and opacity based on iron content and associated minerals. Extremely stable, lightfast, and compatible with all techniques and binders.
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 |
|---|---|---|---|---|---|---|
| Red Ochre |
Key Properties:
| Properties: | Warm red to reddish-brown, earthy tones; Natural: opaque, Burnt: more transparent; Moderate tinting strength; Highly stable and permanent |
| Usage: | Prehistory to present |
| Source: | Natural/Mineral |
| Toxicity: | Non-toxic |
| Fresco: | Yes |
| Tempera: | Yes |
| Oil: | Yes |
| Chemical description: | Primarily hematite (Fe₂O₃) with clay minerals and silica |
| Visualization: | Visible microscopy |
| Identification: | XRF (Fe), Raman, FTIR, SEM-EDS |