How to Make a Plaster Sprig Mold for Creating Jasperware-Inspired Pottery Ross Pollard

Jasperware, an unglazed stoneware ornamented with white clay figures on a colored ground, was developed in the 1770s by the English potter Josiah Wedgwood (1730–1795). One of Wedgwood’s earliest and most profitable uses for Jasperware was in the production of exquisitely detailed portrait medallions. While Wedgwood’s original Jasperware formula remains proprietary, this article outlines an approach to making Jasperware-inspired medallions using ordinary stoneware clay in conjunction with traditional modeling and sprigging techniques. 

Modeling 

The first step in creating a Jasperware-style medallion is to model a bas-relief figure in wax, plasticine, or clay. For this demonstration, I chose to model a 3-inch portrait of Pierre Beaumarchais in the traditional 18th-century manner; with white wax on slate using homemade bone modeling tools (1). Whatever sculpting medium you chose, be sure to avoid undercuts in your model, which could make molding and sprigging difficult. 

Molding 

From the finished model, the next step is to make a plaster sprig mold. To contain the plaster and prevent it from sticking, brush on a thin coating of a release agent and run a clay fence around the perimeter of the modeling board. Next, mix up a batch of plaster and slowly pour it into one corner, allowing it to flow over and around the relief (2). After a few hours, separate the hardened plaster from the model and chamfer any jagged corners with a knife before setting the mold aside to dry (3). 

Sprigging 

When the plaster is dry, select a smooth earthenware clay with good plasticity and press it into the mold cavity (4). Then, use a wooden rib to trim off the surplus, being careful not to tear the impression (5). Gently release the sprig with a spatula, palette knife, or piece of wet clay and slide it onto a damp plaster bat (6). 

the author Ross Pollard is a medallic artist living in rural Minnesota. He holds a degree in art history from the University of Wisconsin-Madison and is self-taught in the art of bas-relief modeling.