The process of fusing powdered or finely ground colored glass onto a glass surface is called enameling. The material is painted or applied to the glass and then fired so it bonds permanently.
Glass enamels are useful for details that cannot be achieved by cutting separate pieces of colored glass. Artists can add faces, hair, folds of clothing, inscriptions, and other fine marks before firing the panel in a kiln.
The term can cause confusion because enamel paint is also used on ceramics and metal. In stained glass, the crucial step is kiln firing, which fixes the glass-based pigment to the sheet rather than leaving a removable surface coating.
Enameling differs from silver staining. Silver stain chemically changes the surface color of glass, often producing yellows, while enamel adds an opaque or translucent glass pigment that is fused in the kiln.