Limoges style enamel, a painterly approach to enamel

Limoges style enamel, called French work in Old Polish, is the most painterly of all enamels. It involves coating metal, usually, with dark enamel and firing it. A drawing of a different colour was then applied over the dark fired layer. 

How exactly was the decoration created?

Decoration with this type of enamel was more like painting. A slightly convex piece of metal was first covered with a transparent layer of enamel, over which coloured layers of enamel paint were then applied. Often the individual layers were overlaid with flake gold or silver to achieve more interesting colour effects.