Bullseye Glass Mold #8629, Round Slumper 11.8"

The Round Slumper 11.8 inch mold from Bullseye Glass (design number 8629) is a slipcast ceramic slumping form that shapes a glass sheet into a round bowl or dish in a single firing. A pre-made glass sheet or fused blank is placed over or set into the form, then heated so the glass softens and settles to the round profile by gravity.

The outer mold dimensions are 11.8 inches in diameter by 1.6 inches deep (30 x 4 cm), which are the measurements to use when checking kiln fit. These molds are handmade by Creative Ceramics in Europe and imported by Bullseye Glass, so dimensions can vary slightly from piece to piece. Measure your mold before cutting glass rather than relying solely on the listed size. The slipcast surface is exceptionally smooth, accepts kiln wash uniformly, and the clay body is formulated to withstand repeated firings without cracking when used properly.

What does the Round Slumper 11.8 inch mold make?
It slumps a glass sheet into a round bowl or dish roughly 11.8 inches across. The finished depth and profile depend on how far the glass settles during firing, which is controlled by temperature and hold time.

How do I size the glass sheet for this mold?
Measure your specific mold before cutting glass, since these are handmade ceramic forms and dimensions can vary slightly from piece to piece. Use the outer dimension of 11.8 inches as a starting reference, then measure your actual mold to confirm.

What COE glass works with this mold?
Any COE. Ceramic slumping forms are COE agnostic, so the same mold works with Bullseye COE90, COE96, or other compatible fusible glass. Match your firing schedule to the glass you are using.

How do I prep the mold before slumping?
Coat the forming surface with a kiln wash or shelf primer and let it dry completely before placing glass. Re coat as needed between firings to ensure clean release.

Specifications

• SKU: 164848
• Manufacturer: Bullseye Glass (model BG8629, design number 8629, item 008629-MOLD-M-EACH; made by Creative Ceramics, Europe)
• Makes: one round glass bowl or dish
• Outer dimensions (for kiln fit): 11.8 inches diameter x 1.6 inches deep (30 x 4 cm)
• Note: molds are handmade and vary slightly in size; measure before cutting glass
• Material: slipcast ceramic, specially formulated clay body, reusable
• Glass: any COE (COE agnostic)

Working Notes

These are guidelines, not guarantees. Every kiln fires a little differently, so test a small run first when the result matters and follow a slumping schedule suited to your glass and kiln.

• Prime the forming surface with a kiln wash or a boron nitride mold primer such as ZYP Boron Nitride Mold Primer, and let it dry completely before placing glass so the finished piece releases cleanly after firing.
• These molds are handmade and dimensions can vary slightly. Measure your mold before cutting glass rather than relying solely on the listed dimensions.
• The mold is COE agnostic. Use a slumping schedule matched to your glass, and adjust the anneal soak temperature for your COE.
• Let the kiln cool fully before removing the slumped piece. Re coat the mold with kiln wash as needed between firings.

Suggested Slumping Schedule (Starting Point)

This is a suggested starting schedule based on Bullseye's published slumping guidance, not a guarantee. Every kiln fires differently. Follow Bullseye's published Suggested Slumping Schedule for your glass and mold depth, visually confirm the slump is complete before cooling, and test a small piece first.

• Ramp at about 300 F per hour up to the slump process temperature. Bullseye's published starting point for this mold is 1190 F; use the lowest temperature that fully forms the glass in your kiln.
• Hold at that temperature for about 5 minutes to let the glass settle into the form. Visually confirm the slump is complete before moving to the next step.
• Drop as fast as possible (AFAP) to the anneal soak temperature: about 900 F for COE90 glass or 950 F for COE96. Hold the anneal soak for about 1 hour.
• Cool at about 100 F per hour from the anneal soak temperature down to 700 F, then cool as fast as possible to room temperature with the kiln door closed.

Helpful downloads: Suggested Slumping Schedules from Bullseye Glass (PDF)

Description updated: July 6, 2026

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