Bullseye Glass Mold #8635, Square Slumper A 8.5"

The Square Slumper A from Bullseye Glass is a ceramic slumping form that shapes a pre-cut glass sheet or fused blank into a square dish or plate. Place the glass on the form, load it into the kiln, and gravity draws the glass down over the surface as it softens. The finished piece follows the profile of the 8.5 inch square form.

The outer mold dimensions are 8.5 inches by 8.5 inches, with a depth of 1.5 inches (22 x 22 x 4 cm). These outer measurements are used to check whether the form fits your kiln shelf. This mold is slipcast from a specially formulated clay body by Creative Ceramics in Europe and imported by Bullseye Glass. The surface accepts kiln wash uniformly and does not crack under repeated proper use. Because each mold is handmade, individual pieces vary slightly in size, so measure the mold before cutting your glass blank.

What does the Square Slumper A make?
It slumps a flat glass sheet or fused blank into a square dish or plate. The form is well suited to decorative dishes, serving plates, or wall art in a square format.

What size glass blank do I need?
Measure the mold in hand before cutting, since handmade dimensions vary slightly from piece to piece. A blank that covers the forming surface and extends slightly past the inner edges allows gravity to draw the glass evenly down over the form during firing.

What COE glass can I use?
Any COE. Ceramic slumping molds are COE agnostic, so this form works with Bullseye COE90, COE96 glass, or other fusible glass. Match your slumping schedule to the glass you are using.

How do I prep the mold before slumping?
Coat the forming surface with a kiln wash such as Hotline Primo Primer and let it dry completely before placing glass on the form. The smooth slipcast surface accepts kiln wash evenly. Re-coat between firings as needed to prevent sticking.

Specifications

• SKU: 2985
• Manufacturer: Bullseye Glass (slipcast by Creative Ceramics in Europe, imported by Bullseye Glass)
• Design number: 8635 (item number 008635)
• Makes: square slumped glass dish or plate
• Outer mold dimensions: 8.5 x 8.5 x 1.5 inches (22 x 22 x 4 cm)
• Note: molds are handmade and vary slightly in size; measure before cutting glass
• Material: slipcast ceramic, reusable
• 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 boron nitride primer such as ZYP Boron Nitride Mold Primer, and let it dry fully before placing glass on the form.
• Measure the mold in hand before cutting your glass blank. The listed dimensions are outer mold dimensions for checking kiln fit; individual handmade pieces vary slightly in size.
• Ramp slowly through the initial heat range to avoid thermal shock, then ramp to the slump temperature and hold until the glass conforms fully to the form.
• Visually confirm the slump is complete before beginning the cool. Adjust the peak temperature or hold time if the glass has not fully settled onto the form.
• The mold is COE agnostic. Adjust the anneal soak temperature to your glass: about 900 F for COE90 or about 950 F for COE96.
• Let the kiln cool fully with the door closed before removing the slumped piece. Re-coat the mold with kiln wash between firings as needed.

Bullseye Suggested Slumping Schedule

This is a suggested starting schedule for slumping 6mm glass in a Paragon GL24, based on Bullseye's published guidance for this mold. It is not a guarantee. Every kiln fires differently and glass styles vary in viscosity. Visually confirm the slump during firing and adjust the schedule for your glass and kiln.

AFAP means as fast as possible, letting the kiln ramp at its maximum natural rate. Segment 2 is the anneal soak; this schedule places it at 900 F for COE90 glass. If using COE96, adjust segment 2 to hold at about 950 F instead. Segment 4 is a natural cool with the kiln door closed.

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

Description updated: July 6, 2026

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