Which technique requires the removal of a base plate after enamel application?

Plique-à-jour is a decorative technique in enameling that involves creating translucent enamel pieces resembling stained glass. For this process, a base plate is initially used to support the enamel during application. After the enamel is applied and set, the base plate is removed, allowing the light to pass through the enamel, enhancing its luminous quality. This distinctive characteristic of plique-à-jour makes it stand out among enameling techniques, as it creates an openwork effect, where color and light interact beautifully without the backing of an opaque surface.

This technique is notably different from the others listed, which have different methods and applications in enamel work. Each of these alternatives maintains their base in some form during the enamel application process, thus creating different visual effects and structural results within the piece.