In answer to a frequently asked question -
 

What is terra sigillata ?

Terra sigillata is the surface I most often use on my work. It is a slip and is not a glaze. Terra sigillata in Greek means "earth seal". It was applied to the black and red figurative amphoras of Greek and Roman times and has a slight sheen rather than a high gloss surface. Terra sigillata is different than other slips in that it is very thin and closely resembles the consistency of milk or half and half. Terra sigillata consists of the finest particles of clay in suspension in water resulting in a very refined slip. It is applied to unfired clay rather than bisque ware and can be applied with a brush or airbrush.

Terra sigillata is made by mixing dry clay plus a deflocculant such as Calgon Bath Beads or sodium silicate. Water is added to this and the resulting mixture is allowed to sit for 48 hours. During that time the heavy paricles sink and the lighter particles remain suspended in water due to the deflocculant. These layers can be clearly seen after 2 days. There is a thin layer of water at the top that can be decanted. The middle mixture is the terra sigillata and this is saved. The layer of heavy particles at the bottom is thrown away. The resulting terra sigillata will vary in color depending on the type of clay used. I use kaolin and OM4 that result in a white terra sigillata. I add Mason stains or oxides to the white mixture to create a variety of colors.