Enameling is the process of firing powdered or finely ground glass onto a stained-glass surface to create a decorative coating. The material, called enamel, is mixed with a medium, applied to the glass, and heated until it fuses.
Glass painters use enamels for details that cannot be achieved by color alone. They can create facial features, hair, folds in clothing, shadows, lettering, and delicate patterns. After firing, the coating becomes part of the glass surface rather than remaining a loose powder.
Medieval glaziers used related painted-glass techniques, often applying dark pigment to model figures before firing the pieces. Modern studios may use several enamel firings, but excessive heat can affect earlier layers or distort the glass.
Enameling differs from slumping, which bends glass in a kiln, and annealing, which carefully cools glass to reduce internal stress. Those processes change shape or strength rather than add a pictorial coating.