The Round Plate 12.8 inch mold from Bullseye Glass (design #8928) is a ceramic slumping form that shapes a pre-made glass sheet or fused blank into a round plate roughly 12.8 inches across. A cut circle or fused blank is placed over the form and the kiln is brought to slumping temperature, where gravity draws the softened glass down over the shallow form to produce a gently curved plate.
The outer mold dimensions are 12.8 inches in diameter by 0.7 inches deep (33 by 2 cm). Bullseye provides these as kiln fit dimensions. Because the forms are slipcast from a specially formulated clay body by Creative Ceramics in Europe and imported by Bullseye Glass, individual pieces vary slightly in size, so measure your mold before cutting glass. The surface is exceptionally smooth, accepts kiln wash evenly, and the ceramic body holds up under repeated proper use.
What does the Round Plate 12.8 inch mold make?
How is glass slumped on this mold? Hotline Primo Primer and allow it to dry completely. Place a pre-cut glass circle or fused blank on top of the mold, load it into the kiln, and follow a slow ramp slumping schedule. The glass softens and settles into the plate profile under gravity at slumping temperature.
What COE glass works with this mold?
Do I need to prime the mold before each use?
Specifications
SKU: 156614Manufacturer: Bullseye Glass (BG8928, design #8928, item 008928-MOLD-M-EACH); made by Creative Ceramics in EuropeMakes: 1 round plate per firingMold size: 12.8 in diameter x 0.7 in deep (33 x 2 cm), outer dimensions for kiln fitMaterial: ceramic slumping form, slipcast from a specially formulated clay body, reusableGlass: any COE (COE agnostic)
Working Notes
These are guidelines, not guarantees. Every kiln fires a little differently, so test a small piece first when the result matters and follow a slumping schedule suited to your glass and kiln.
Coat the forming surface with kiln wash or a boron nitride mold primer such as ZYP Boron Nitride Mold Primer , and let it dry completely before placing glass.
The outer dimensions (12.8 in diameter by 0.7 in deep) are listed by Bullseye for kiln fit. These molds are handmade and vary slightly in size, so measure yours before cutting glass to fit.
Place your pre-cut glass circle or fused blank on top of the mold, centered on the form. Do not force the glass into position.
Ramp slowly to slumping temperature and visually confirm the slump during firing. Let the kiln cool fully before removing the finished plate.
The mold is COE agnostic. Adjust the anneal soak to your glass: about 900 F for COE90 or 950 F for COE96.
Re-coat the forming surface with kiln wash between firings as needed.
Bullseye Suggested Slumping Schedule
This is a suggested starting schedule based on Bullseye's guidance for slumping 6mm pieces in a Paragon GL24 kiln. It is not a guarantee. Every kiln fires differently, glass styles vary in viscosity, and mold depth affects the result. Visually confirm the slump during firing and adjust the schedule for your glass and kiln.
Segment Rate (F/hr) Temp (F) Hold 1 (slump) 300 1225 1:30 2 (anneal soak) AFAP 900 1:00 3 (anneal cool) 100 700 none 4 (cool) AFAP 70 none
AFAP means as fast as possible. Segment 4 is the final cool to room temperature: let the kiln cool at its natural rate with the door closed. The 900 F anneal soak in segment 2 is suited to COE90 glass. If using COE96, adjust that soak to 950 F.
Helpful downloads: Suggested Slumping Schedules from Bullseye Glass (PDF)
Description updated: July 6, 2026
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