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Terra Sigillata Slip Recipe

Terra Sigillata is a red slip glaze used initially by the Romans. It is made of fine, decanted particles of red clay. This is an excellent method to teach students as it is very similar to techniques used by Native American (Pueblo) potters. It is especially applicable to the study of San Ildefonso potter Maria Martinez.


  • 11 pounds Newman Red or Red Ball Clay (dry)
  • 3 gallons water
  • 25 grams soda ash (acts as flux to lower firing temperature)


  1. Place water in a bucket.
  2. Add dry clay.
  3. Stir.
  4. Add soda ash.
  5. Mix well.
  6. Leave the mixture overnight, then drain off the watery top third and discard. Save the middle third for use as a slip and discard the coarser bottom third.

Application and Burnishing
Terra Sigillata slip has the advantage of being applied to greenware or bisqueware.

Use a wide (1 in.) flat brush to apply a thin coat over the pot surface and burnish with a soft cotton cloth. Burnish much in the same way as you would polish an apple.

For larger pots, it is best to apply the slip to a three inch area at a time, burnishing as you go.

Repeat with a second coating of slip and burnish. The two thin coats are better than one heavy coat, which could crack off.