The resonators
In the bygone days, the resonators were embellished with magnificent decorative motifs (e.g. the rich floral decoration on the 17th century bin kept at the Musée de la Musique in Paris, the last of the following images).
The gourds were first covered with a silica-based film, and would then sometimes get a metallic undercoat (tin), probably intended to reflect the luminous intensity of the tint on which the ornamental motifs – made from organic or vegetable-based pigments - would then be applied. In our time, these resonators are coated with a fine film and then with a tinted varnish to give it the shiny, translucent appearance of a lacquer.