Sgraffito is basically a simple decorative technique but can reach very elaborate standards in designs and craftsmanship. The method is to put slip over clay then scratch the slip off and make a design by revealing the clay body underneath. The color of the slip against the color of the clay accentuates the design. The slip should be made up with the same clay as the body so the shrinking is compatible.
Many of the clay fragments found in archaeological sites are sgraffito and they show either a representation of what was in the jars or served as decorative elements with style and originality, sometimes they had pictorial motifs.
Photos lent by Anna G. Capell