This recipe is based on Kari Radasch’s formulation. Mix contents thoroughly in a 5-gallon bucket with a drill and place on a tabletop. Let the mixture sit for 10 hours. The water, terra sigillata, and heavier slip particles should separate into 3 parts. The next step is to siphon the center layer (which is the terra sigillata) into a bucket on the ground with the help of gravity. Store the terra sigillata in an air-tight container until needed. I make 5–6 batches at a time because the older the terra sigillata is, the easier it is to work with—a very helpful tip I learned from Mark Arnold. When adding colorants/Mason stains to small batches, I use 1 teaspoon to 1⁄2 tablespoon of various Mason stains to 11⁄2 cups of terra sigillata to achieve my desired color tint. Measuring the Mason stains by volume rather than by weight yields a wider variety of colors from batch to batch.
I consistently use the following Mason stains to
make colored terra sigillatas:
4150 Red/Pink, 4200 Orange, 6236 Chartreuse, 6242 Bermuda, 6315 Turquoise, 6343 Mediterranean, and 6363 Sky Blue.
This recipe was shared by Megs LeVesseur in the May 2022 issue of Ceramics Monthly.