What do we call the medieval practice of decorating books with gold leaf?

The story behind the answer

This is the technique of applying thin sheets of real gold to manuscript pages—often on initials, borders, and halos—then burnishing them to a mirror-like shine. Artisans laid a sticky ground such as gesso or glair, placed the leaf, and polished it with an agate or dogtooth burnisher so the page would catch candlelight and suggest divine radiance and royal prestige. Gold was prized because it doesn’t tarnish, preserving brilliance for centuries.

By contrast, “illumination” is the broader art of decorating manuscripts with paint and sometimes gold; “tooling” refers to stamped patterns in leather (especially on bindings); and “embossing” creates raised relief. Lavish medieval works like Carolingian and Gothic Psalters exemplify this glittering craft.