Terra Sigillatta

Terra sigillatta, or terra sig, is basically a thin clay slip.  In Greek it means "earth seal."  It was used by the ancient Greeks on their red and black wears.  Terra sig is made by separating the fine particles from the heavier ones.  This is done by mixing a dry clay body with water and a deflocculant, such as sodium silicate.   The mixture is allowed to set and settle out for 6-48 hours.  The deflocculant prevents the smallest particles from settling with the larger ones.  After a number of hours the thin particles are siphoned off becoming terra sig.  At this point it is the consistency of milk and is applied to bone dry pieces by means of brushing, dipping, or spraying.