The Large Cone Bowl mold from Bullseye Glass, design number 8975, is a steep-sided cone slumping form. A pre-cut or pre-fused glass blank is placed on the top rim of the cone, then fired so the glass softens and drapes down into the steep cone shape by gravity. The finished piece has a tall, tapered profile with a narrow base, suited to decorative bowls, votive holders, and display vessels.
The outer mold dimensions are 11.5 inches by 3.4 inches (29 x 9 cm). These figures are provided for kiln fit planning only. Because this mold is handmade, slipcast from a specially formulated clay body at Creative Ceramics in Europe and imported by Bullseye Glass, individual molds vary slightly in size. Measure your specific mold before cutting glass. The forming surface is exceptionally smooth, accepts kiln wash uniformly, and holds up under repeated proper use. Like all ceramic slumping forms, this mold is COE agnostic and works with COE90, COE96, or any other fusible glass.
What does the Large Cone Bowl mold make?
How do I cut glass for this mold?
How do I set this mold up in the kiln?
How often do I need to re-prime this mold?
Specifications
SKU: 9274Manufacturer: Bullseye Glass (store code BG8975, design #8975, item 008975-MOLD-M-EACH; made by Creative Ceramics, Europe)Mold type: steep-sided cone slumping formOuter dimensions: 11.5 in x 3.4 in (29 x 9 cm), for kiln fit only; handmade, measure before cutting glassMaterial: slipcast ceramic, reusableGlass: any COE (COE agnostic)Kiln setup: elevate on 2 in (5 cm) posts, center and level in kiln
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 Bullseye's published guidance for your glass and mold depth.
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.
Because of the steep cone geometry, re-prime the forming surface every 2 to 3 firings, not just when the coating looks worn.
Elevate the mold on 2 inch (5 cm) posts, center it in the kiln, and level both the mold and the glass before firing to promote even heating and slumping.
Cut glass to the diameter of the top rim, or up to 1/16 inch (1.5 mm) larger all around, so the rim supports the glass as slumping begins. Measure your mold before cutting, since each mold is handmade and varies slightly in size.
The mold is COE agnostic. Match your slumping schedule to the glass you are using, and adjust the anneal soak temperature for your COE.
Let the kiln cool fully before removing the slumped piece. Inspect the kiln wash coating after each firing and re-prime as needed before the next run.
Suggested Slumping Schedule
This is a suggested starting schedule based on Bullseye's cone bowl tip sheet guidance, not a guarantee. Steep-sided molds heat unevenly, so visually confirm the slump is complete before cooling, and adjust the schedule for your glass and kiln. Follow Bullseye's published Suggested Slumping Schedule for your glass and test a small piece first.
Ramp at 300 F per hour to 1200 F and hold for 30 minutes. Bullseye uses this lower temperature hold to begin the slump and promote a uniform drop into the steep form.
Ramp at 300 F per hour to 1225 F and hold for about 1 hour, longer than a standard shallow slump requires, so the glass settles fully into the steep cone. Visually confirm the slump is complete before proceeding to cool.
Cool as fast as possible (AFAP) to an anneal soak of about 900 F for COE90 glass (or about 950 F for COE96) and hold for about 1 hour.
Cool at 100 F per hour from the anneal soak temperature down to 700 F.
Cool as fast as possible (AFAP) from 700 F to room temperature.
Helpful downloads: Suggested Slumping Schedules from Bullseye Glass (PDF)
Description updated: July 6, 2026
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