Giustiniani tile from the 18th century, the progenitor Neapolitan manufacture.

The imitation of the Mosaic

The frequency of squared backgrounds demonstrates how much they took inspiration from the mosaics that emerged from the excavations of the Vesuvian cities. The double row of pure squares allude to the mosaic floors of the Roman world: this decoration is obtained by means of black graffiti, applied with a brush on the underlying light colored enamel which thus emerges again. The mosaic decoration therefore required a freehand intervention which traced a series of threads for the rendering of the small squares which were to emulate the mosaic tiles.

taken from the book by "Matilde Romito"
ENAMELS AND MEDITERRANEAN COLOURS
Province of Salerno
Salerno Study Center "Raffaele Guariglia"
March 2003