|Water (in parts)||2.00|
|Clay (in parts)||1.00|
|OM 4 Ball Clay Base Terra Sigillata (in cups)||1.00|
|Cobalt Carbonate (in tsp)||0.25|
|Newman Red Base Terra Sigillata (in cups)||0.50|
Mix 1 part clay to 2 parts water, blend well with drill mixer. Add 0.25–0.5% (of the dry weight of the clay) of a deflocculant (sodium silicate or Darvan 7), then drill mix again. Allow heavier (red clay) terra sigillatas to settle for at least 6–8 hours, and lighter clays/ball clays to settle for 24–48 hours. After the mixture has settled into distinct layers, siphon out the middle section of the mixture. This is the terra sigillata.
Measurements for colorants are per 8 oz/1 cup liquid terra sigillata. These recipes have broad firing range and also work well in wood, soda, salt, and atmospheric kilns.This recipe was shared by Rhonda Willers in the November/December 2020 issue of Pottery Making Illustrated.