Bullseye Glass Mold #8648, Square Bowl Double Curve 11.8"

The Square Bowl Double Curve mold from Bullseye Glass (design number 8648) slumps a flat glass blank into a square bowl with a compound curved profile. The outer mold measures 11.8 by 11.8 inches with a depth of 2.1 inches, making it suitable for mid-size and larger kilns and well suited to functional bowls, decorative serving pieces, and display work.

The mold is slipcast from a specially formulated clay body by Creative Ceramics in Europe and imported by Bullseye Glass. The surface is exceptionally smooth, accepts kiln wash uniformly, and holds up under repeated proper use. To use it, coat the forming surface with kiln wash, set a pre-cut or pre-fired glass blank over the mold, and heat until the glass softens and conforms to the form by gravity. Because these molds are handmade, they vary slightly in size from piece to piece, so measure your mold before cutting your glass blank.

What does this mold make?
It slumps one square bowl with a double curve profile. The outer mold dimensions are 11.8 by 11.8 inches with a depth of 2.1 inches (30 x 30 x 5 cm).

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

How do I size my glass blank?
Measure the mold before cutting your glass. The listed outer dimensions are for checking kiln fit, not for sizing your blank. These forms are handmade and vary slightly, so measure yours directly and cut or fuse a blank to fit.

How do I prepare the mold?
Coat the forming surface with a kiln wash such as Hotline Primo Primer and let it dry fully before placing your glass. The surface accepts kiln wash uniformly. Recoat as needed between firings.

Specifications

• SKU: 159913
• Manufacturer: Bullseye Glass (made by Creative Ceramics, Europe; model BG8648, design number 8648, item number 008648-MOLD-M-EACH)
• Makes: 1 square bowl with double curve
• Outer mold dimensions: 11.8 x 11.8 x 2.1 inches (30 x 30 x 5 cm)
• Material: slipcast ceramic slumping form, reusable
• Glass: any COE (COE agnostic)

Working Notes

These are guidelines, not guarantees. Every kiln fires a little differently, so test with your glass and kiln before committing to a full piece and follow a slumping schedule suited to your glass.

• Measure the mold before cutting your glass blank. These forms are handmade and vary slightly in size. The outer dimensions are a guide for kiln fit only.
• Coat the forming surface with kiln wash and let it dry completely before placing your glass. You may also use a boron nitride mold primer such as ZYP Boron Nitride Mold Primer. Recoat between firings as needed.
• Place your glass flat over or into the mold. Use a controlled ramp rate to avoid thermal shock, and hold at the slump temperature until the glass fully conforms to the form.
• This mold is COE agnostic. Adjust the anneal soak temperature to match your glass: about 900 F for COE90 or about 950 F for COE96.
• Let the kiln cool fully before removing the finished piece. Recoat the mold surface with kiln wash as needed between firings.

Bullseye Suggested Slumping Schedule

This is a suggested starting schedule based on slumping 6mm pieces in a Paragon GL24 kiln. 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, kiln, and blank thickness.

AFAP means as fast as possible. Segment 2 is the anneal soak at 900 F, suited to COE90 glass. If using COE96, adjust the anneal soak to approximately 950 F. Segment 4 lets the kiln cool to room temperature at its natural rate with the door closed.

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

Description updated: July 6, 2026

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