Set aside the broken pieces until they are completely dry. Use a fine-tip paintbrush to draw a thin line of water along the broken edges. Dip the paintbrush in slip, and apply a bead of slip along the break (shown above). Press the pieces together, and set them aside to dry completely. Add additional layers of slip until the join is no longer visible. Use a moist, fine-tip paintbrush to smooth any imperfections. Allow the piece to dry completely before firing.
Use oil paste to repair breaks in fired clay. If using a commercial brand (such as Art Clay Silver Oil Paste), follow the manufacturer’s instructions for application and firing. Alternatively, you can make your own oil paste.