The stained-glass technique of painting silver compounds onto glass to create yellow or amber tones is called silver stain.
Silver stain was developed in the early fourteenth century and became an important medieval method for adding color without using a separate piece of glass. A silver compound is applied to the surface, then fired in a kiln. The treatment penetrates the glass and produces yellow, gold, or amber shades, depending on the formulation and firing conditions.
This invention greatly expanded the range of imagery available to glass painters. It allowed details such as hair, halos, borders, and highlights to be placed on existing clear or colored pieces. The technique is especially important in late medieval and Renaissance stained glass.
Silver stain is not the same as grisaille. Grisaille is a monochrome painted-glass style using opaque or semi-opaque paint, while silver stain chemically colors the glass during firing.