Basic Terra Sigillata Formula
1 liter water
400 grams clay
4 grams soda ash
Judith Motzkin Terra Sigillata
14 C Water
7.5 grams Deflocculant (calgonite, soda ash, sodium silicate, sodium hexametaphosphate)
1080 grams OM#4 Ball Clay
60 grams Bentonite
260 grams EPK
Dissolve deflocculant in the water.
Dry mix bentonite with other clay to avoid bentonite clumps.
Sift clay into water.
Allow to slake, fully wetting the clay, before mixing.
Mix then pass through a fine sieve.
Let settle undisturbed for 22 hours.
Siphon off the top third or until you reach the visible separation point.
Add 7% of these minerals for colors:
Copper carb= warm grey\
Or experiment with Mason Stains of your choice.
Ball milling, while not necessary, will give you more and finer slip.