Black Iron Oxide Pigment

Black Iron Oxide (Fe₃O₄) – Deep Black Mineral Pigment

TerraChrom Black Iron Oxide is a high-quality synthetic mineral pigment valued for its deep black colour, strong colouring ability, and versatility in paints, coatings, and mineral-based finishes.

Also known as Pigment Black 11 (PBk11), black iron oxide is widely used to create rich black tones and darken other colours. Its fine, micronised powder form allows it to be incorporated into a variety of compatible paint and coating formulations.

This pigment contains more than 96.8% Fe₃O₄ (typical reference value) and offers consistent colouring performance. It is suitable for both interior and exterior applications when used in an appropriately formulated binder system.

Key Features

• Deep, rich black colour

• High iron oxide content (>96.8% Fe₃O₄, typical)

• Fine, micronised powder

• Consistent colour and tinting strength

• Suitable for water-based and oil-based paint formulations*

• Can be used in cement, concrete, plasters, and mineral finishes*

• Suitable for interior and exterior applications*

*Performance and compatibility depend on the binder, formulation, pigment concentration, substrate, and application conditions.

Recommended Uses

Black iron oxide can be used in a wide range of paint and mineral applications, including:

• Acrylic, oil, and watercolour paints

• Limewash and mineral paints

• Decorative plasters and stucco

• Concrete and cement colouring

• Primers, coatings, and sealers

• Interior and exterior decorative finishes

It is commonly added to produce deep black finishes, dark grey tones, and muted colours, either on its own or in combination with other pigments.

Product photographs illustrate results in concrete (10% pigment ratio), Cement All (2% and 10% pigment ratios), and wall samples finished with TerraChrom lime paint. These examples are illustrative; final colour depends on the formulation, dosage, substrate, and application.

Technical Information

Chemical name: Iron(II,III) oxide (Fe₃O₄)
Pigment type: Micronised synthetic black iron oxide
Colour Index: Pigment Black 11 (C.I. 77499)
CAS number: 1317-61-9
Appearance: Fine black powder
Fe₃O₄ content: >96.8% (typical reference value)
Density: Approximately 4.6 g/cm³
Oil absorption: Approximately 21 g/100 g pigment
pH: 5–8
Predominant particle size: Approximately 0.2 µm
Relative tinting strength: 95–105% against the specified reference standard
Country of origin: Germany

Using Black Iron Oxide in Paint

Black iron oxide can be added to compatible paints and coatings to create black, charcoal, and grey shades. The depth of colour depends on the amount of pigment added, the colour of the base paint, and the binder formulation.

Small amounts can be used to darken existing colours or produce subtle grey tones, while higher pigment concentrations can create stronger black finishes.

Suggested starting quantities for natural paints:

• 10–20 mL per litre of paint: For subtle darkening or light grey tones in a white base.

• 20–40 mL per litre of paint: For more pronounced grey or charcoal tones.

• 40–75 mL per litre of paint: For stronger, darker colour development.

For formulations measured by weight, 2% pigment by weight is a useful initial trial concentration. Higher concentrations, including 5% and 10%, may be tested where the binder and intended application can accommodate them.

These quantities are practical starting points for small-batch testing, not established dosage specifications or maximum limits. Pigment concentration alone does not determine the final colour, and excessive pigment loading may affect adhesion, durability, or surface finish.

Mixing Example

For 1 litre of water-based natural paint:

1. Measure approximately 20 mL of black iron oxide powder into a small mixing container.

2. Add approximately 20 mL of lukewarm water, a little at a time, stirring continuously to form a smooth paste.

3. Mix thoroughly until the pigment is evenly dispersed and free of visible lumps. Add a small amount of additional water if needed.

4. Gradually incorporate the pigment paste into 1 litre of prepared paint, stirring thoroughly to distribute the colour evenly.

5. Apply a small test sample and allow it to dry completely before evaluating the final shade.

For a darker finish, gradually increase the pigment concentration in subsequent test batches.

Note: This mixing method is intended as a practical starting point for compatible water-based natural paints. Results vary depending on the binder and formulation. For oil-based paints, disperse the pigment using an appropriate compatible medium rather than water.

Creating the Perfect Black

To achieve your desired black or charcoal shade, start with a compatible untinted or lightly coloured base paint and add black iron oxide gradually.

1. Prepare a small test batch using a measured quantity of pigment.

2. Apply the mixture to a sample surface and allow it to dry completely.

3. Evaluate the colour under natural lighting.

4. Adjust the pigment concentration until the desired depth and tone are achieved.

For the deepest black, choose a base formulation suitable for high pigment loading. A white base may produce grey rather than a true black, even with additional pigment.

Keeping a record of your pigment ratios will help you reproduce the same shade in future batches.

Safety

Black iron oxide is a fine mineral powder that may generate airborne dust during handling. Although not classified as hazardous under the Canadian Hazardous Products Regulations (HPR), appropriate handling precautions should be followed.

• Avoid breathing dust and minimize dust generation.

• Work in a well-ventilated area.

• Use appropriate respiratory protection when necessary.

• Avoid contact with eyes and wash hands after handling.

• Store in a cool, dry place in tightly closed containers.

• Avoid temperatures above 80°C, as excessive heat can cause oxidation, irreversible colour changes, and heat generation.

• Keep away from combustible materials and excessive heat.

• Keep out of reach of children.

Refer to the current TerraChrom Safety Data Sheet (SDS) for complete handling, storage, and safety information.

Technical Documents

Safety Data Sheet: English | Français

Technical Data Sheet: English | Français