Pigments and Colorants

When discussing almost any archaeological artifact, color is an important characteristic. Unfortunately, there is often confusion between what constitutes a colorant and what constitutes a pigment. These terms are often used interchangeably, but they have different meanings. Colorants are compounds that impart color to a substance. A colorant may be a pigment, a dye, or an ionized solution. Mineral colorants have definite chemical compositions, recognizable physical characteristics (see Chap. 2), and consistent chemical behavior. Organic colorants contain carbon with hydrogen, oxygen, nitrogen, and sulfur with other minor elements. They are derived from vegetable sources or made synthetically. Although a few organic colorants are stable and basically permanent, in general they tend to be fugitive. The key concept in determining a pigment versus a colorant is its solubility. Only insoluble materials such as minerals are pigments.