terra sigillata

Literally translated as "sealed earth." Ultrarefined clay slip, made by deflocculating a clay in water so the heavy particles settle, leaving the finer particles in suspension to be decanted as terra sigillata. Can give a soft sheen when applied to bone-dry wares and, if polished or burnished while still damp, may give a high gloss. All ancient Greek red-black pottery and Roman red wares were finished with this technique, without the use of glaze.