Color Strength

As well as color, color strength (or tinctorial strength) must be considered when choosing a pigment. Color strength is the facility with which a colored pigment maintains its characteristic color when mixed with another pigment. The higher the color strength, the less pigment is required to achieve a standard depth of shade.

Chemical structure is one of the factors that influence the color strength of a pigment.

• In organic pigments, color strength depends on the ability to absorb certain wavelengths of light. Highly conjugated molecules and highly aromatic ones show increased color strength.
• Inorganic pigments that are colored due to having metals in two valency states, show high color strength. In contrast, those that have a cation trapped in a crystal lattice are weakly colored.

Particle size also influences the color strength of a pigment. Higher color strength is obtained with smaller particles. Manufacturing conditions are the main factor that influences the particle size of pigment crystals. Pigment manufacturers play a crucial role:

• They can reduce the size of the particles by preventing the growth of crystals during synthesis,
• and they can increase color strength by efficient dispersion.

Pigment dispersion will also take a major role in the color strengh of the paint. Indeed, it will impart colloidal stability to the finer particles, avoiding their flocculation and using their full intrinsic color strength.