How to Repair a Glass Slump Mold

Repair glass slumping molds with refractory cement.

Glass slumping molds serve as a form for a sheet of glass that slumps or sags into the mold as it's heated in a kiln. Molds are typically made of ceramic. Over time, they may chip and crack. Complete fractures are impossible to fix, but cracks and chips can and should be repaired. The glass will melt into the crack or chipped area, resulting in a defect. Since the slumping mold is exposed to temperatures in excess of 1,000 degrees Fahrenheit, glue or putty won't suffice. You must use a heat-safe refractory cement. Opt for a fine-grain cement designed specifically for use on glass slumping molds. Glass slumping is sometimes referred to as "glass sagging."

Things You'll Need

• Water
• Refractory cement
• Putty knife
• Sponge
• Fine-grit sandpaper

Instructions

1. Rinse the mold to remove dust particles. Allow the mold to air dry.

2. Apply refractory cement to the chip or crack using a small putty knife. Press the cement into the crack or chip by running the putty knife over the cement in several different directions.

3. Wipe away excess cement with a damp sponge. Thoroughly rinse the sponge immediately after wiping the mold.

4. Allow the refractory cement to dry. Consult the product packaging for the recommended drying time.

5. Don a protective face mask.

6. Sand the cement patch to smooth it and to ensure it blends seamlessly with the surrounding area.

7. Wipe the inside of the mold with a damp sponge before applying glass separator for the next slumping project.

Tips & Warnings

• Always apply glass separator to the mold before slumping glass. Otherwise, the glass will stick to the mold.

• If the mold has lots of indentations, you may opt to use a finger to apply the refractory cement to avoid filling in indentations that are supposed to be present on the mold.

• Never use glue to repair a glass slumping mold. It will be destroyed by the high heat.

• The refractory cement is sold under different names like Amaco Bisque Fix and Slumpy's Magic Mender. You can purchase these products at pottery supply retailers.

References

• Slumpy's: Slump's Ceramic Mold Care Instructions