Bullseye Glass Mold #8924, Rectangular Slumper

The Rectangular Slumper mold #8924 from Bullseye Glass is a slumping form that shapes a pre-made flat glass sheet or fused blank into a gently curved rectangular panel. You place the glass over the mold, heat the kiln until the glass softens, and gravity does the rest, pulling the piece down to follow the form. The finished shape works well for decorative trays, serving dishes, window accent panels, and similar rectangular slumped pieces.

The outer mold dimensions are 12.2 inches by 7.4 inches by 1.7 inches deep (31 x 19 x 4 cm). These outer measurements are provided for checking kiln fit and planning your glass cut. Each mold is handmade by Creative Ceramics in Europe from a specially formulated clay body, so individual pieces vary slightly in size. Measure your specific mold before cutting glass. The surface is exceptionally smooth, accepts kiln wash uniformly, and holds up to repeated proper use without cracking.

What does this mold make?
It shapes a flat glass blank into a shallow curved rectangular panel. The piece follows the mold contour as it softens in the kiln, producing a gently slumped rectangular form suitable for trays, panels, and decorative pieces.

What COE glass can I use?
Any COE. Ceramic slumping forms are COE agnostic, so the same mold works with COE96, COE90, or other fusible glass. Match your firing schedule and anneal temperature to the glass you are using.

How do I size my glass blank for this mold?
The outer mold dimensions are 12.2 x 7.4 inches, but each mold is handmade and varies slightly in size. Measure your specific piece before cutting glass, and test fit the blank cold before loading the kiln.

How do I prep the mold before slumping?
Coat the forming surface with a kiln wash such as Hotline Primo Primer or a shelf primer and let it dry completely before placing glass on the mold. The surface accepts kiln wash uniformly. Re-coat between firings as needed.

Specifications

• SKU: 152853
• Manufacturer: Bullseye Glass (made by Creative Ceramics, imported and sold by Bullseye)
• Model code: BG8924 (Bullseye design #8924, item 008924-MOLD-M-EACH)
• Makes: shallow rectangular slumped glass panels
• Outer mold dimensions: 12.2 x 7.4 x 1.7 in (31 x 19 x 4 cm)
• Material: slipcast clay body, reusable slumping form
• Glass: 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 shelf primer such as ZYP Boron Nitride Mold Primer and let it dry completely before placing glass on the mold.
• Because each mold is handmade and varies slightly in size, measure your specific piece before cutting glass. Test fit the blank cold before loading the kiln.
• The mold is COE agnostic. Use a slumping schedule matched to your glass, and adjust the anneal soak temperature for your COE: about 900 F for COE90 or 950 F for COE96.
• Visually confirm the slump during firing if your kiln allows it. The glass should settle fully into the form before you begin cooling.
• Let the kiln cool fully before removing the slumped piece. Re-coat the mold surface with kiln wash as needed between firings.

Bullseye Suggested Slumping Schedule

This schedule is a suggested starting point based on slumping 6mm pieces in a Paragon GL24, not a guarantee. Every kiln fires differently. Follow Bullseye's published Suggested Slumping Schedule for your glass and mold depth, and test a small piece first.

AFAP means as fast as possible, letting the kiln drop at its natural rate. Segment 4 is the final cool to room temperature with the door closed. Adjust the Segment 2 anneal soak temperature for your glass COE if needed.

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

Description updated: July 6, 2026

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