According to Wikipedia:
Sgraffito ("scratched", plural Scraffiti and often also written Scraffito) is a technique either of wall decor, produced by applying layers of plaster tinted in contrasting colors to a moistened surface, or in ceramics, by applying to an unfired ceramic body two successive layers of contrasting slip, and then in either case scratching so as to produce an outline drawing. A combed wall surface is produced by dragging a comblike tool over a prepared surface, producing stripes or waves.
This particular decorative technique applied to the wall buildings, was widespread trough Italy (specially in central regions) during the Renaissance. However this particular technique flourished during the last decade of the XIX Century in France and in Belgium. In this latter Country, several sgraffites were used to decorate several Art Nouveau building, till they could be considered one of the specific characteristic of Belgian Art Nouveau.
Probably, the most famous example of sgraffito in Bruxelles is the famous Maison Cauchie. Build in 1905, the building was the residence house of the architect Paul Cauchie and of her wife, the painter and illustrator Catherine Voet, known as Lina. The house is fully decorated with the sgraffito technique and the overall impression is eye-capturer. The fact is that the house itself, and mainly the decorations, are used as a sort of advertising for the work of the two artists. So combining an outstanding and fascinating catching female decoration:
With a sort of visit card in pure sgraffito style:
Apart the famous Cauchie house the technique of sgraffito is really omnipresent in the production of the Belgian Art Nouveau architecture and façade design.
Sinuous female figures:
Scenes, mostly with gold colored shapes, which gives a very special effect, when illuminated by the sun:
Some of them, are realized using few colors, mainly reds, providing a warm and intimate vintage effect, resembling really the Renaissance’s houses style:
and, finally, the pure geometrical abstract designs, which translate into the technique of the sgraffito, the aesthetic researches performed during the same years by Henry van de Velde and, moreover, by the most representative architect of the Belgian Art Nouveau, Victor Horta: