Interference pigments having a blue mass tone

A process for preparing a pigment comprising a platelet-shaped carrier material coated with

• (i) a first layer of a colorless, transparent metal oxide of a first refractive index,
• (ii) a second layer of colorless, transparent metal oxide of a second refractive index lower than the first refractive index and
• (iii) a third, outer layer of cobalt aluminate, cobalt-containing glass, tungsten oxide or cobalt oxide,
• said process comprising:
• suspending the platelet-shaped carrier material in water, heating the suspension, adding a water-soluble metal compound at a pH which is appropriate for hydrolysis, so that a metal oxide hydrate a first refractive index is precipitated onto the suspended carrier, the pH required for the precipitation of the respective metal oxide hydrate being established and kept constant by simultaneous addition of acid or base,
• subsequently adjusting the pH with a base to 4 to 10 and adding a water-soluble metal compound, so that a metal hydrate of refractive index lower than the first refractive index is precipitated onto the suspended carrier, the pH being kept constant by simultaneous addition of acid or base, and
• subsequently washing, drying and calcining resulting product,
• suspending the product in water and coating at a pH of from 3 to 10 with cobalt oxide hydrate, cobalt and aluminum oxide hydrate or cobalt and silicon oxide hydrate by addition and hydrolysis of the corresponding water-soluble metal compounds, the pH being kept constant by simultaneous addition of a base, or coating with an alkali metal tungstate and reducing said tungstate, and
• subsequently washing, drying and calcining product.