Rublev Colours Natural Black Oxide is a dense, opaque mineral black made from magnetite (Fe3O4), valued for its permanent colour, neutral to slightly cool undertone, and clean handling. Unlike many carbon blacks, black oxide is non-greasy, wets easily, and mixes predictably, making it a practical choice when you need a deep black that does not feel sooty or oily in paint films.

Black oxide is a comparatively modern addition to artists’ palettes (not widely used before the 19th century) and is prized today for its stability and versatility. As a true iron oxide mineral, it is absolutely permanent and broadly compatible with other pigments across oil, acrylic, watercolour, and other common binders. It is excellent for strong value structure, neutral greys, underpainting, and reducing chroma without the softness and sheen sometimes associated with carbon blacks.

Natural Black Oxide has a relatively low oil demand, forming a stiff paste when mulled, and it typically yields a hard, fairly flexible paint film in oil.

Key specs

• Colour Index: PBk 11 (77499)

• Pigment type: Natural inorganic (magnetite black iron oxide)

• Chemical formula: Fe3O4

• ASTM lightfastness: I (Acrylic, Oil, Watercolour)

• Opacity: Opaque

• Average particle size (D50): 0.30 microns (cubic)

• Density: 5.0 g/cm3

• Oil absorption: commonly 10 to 15 g oil / 100 g pigment (forms a stiff paste)

• Size: 100g

Handling and safety
Not considered toxic, but as with all dry pigments avoid inhaling dust and avoid ingestion or prolonged skin contact. Use good ventilation and a dust mask when handling powder.