Definition of a Pigment
A pigment is a material that selectively absorbs certain wavelengths of light and reflects others, thereby imparting color to a substance. Unlike dyes, which are soluble and chemically bond with the material, pigments are finely ground solid particles that remain insoluble and dispersed within a binder or medium.
How Pigments Create Color
When white light (which contains all colors of the visible spectrum) strikes a surface containing a pigment, the pigment absorbs specific wavelengths of light. The remaining, unabsorbed wavelengths are then reflected or transmitted, and these are the colors that our eyes perceive. For instance, a red pigment absorbs most non-red wavelengths, reflecting primarily red light.
Examples in Nature and Industry
In nature, chlorophyll is a biological pigment that gives plants their green color by absorbing red and blue light. Melanin is another natural pigment responsible for the color of skin, hair, and eyes. Industrially, pigments like titanium dioxide (white), iron oxides (reds, yellows, browns), and phthalocyanine blue are widely used in paints, plastics, inks, and cosmetics due to their excellent opacity and lightfastness.
Key Properties and Applications
Important properties of pigments include their hue (color), opacity (ability to cover), tinting strength, lightfastness (resistance to fading), and chemical stability. Because they are insoluble, pigments are often preferred over dyes for applications requiring durability against environmental factors, high coverage, and long-lasting color, making them crucial for exterior paints and fine art.