The Square Slumper B with Flat Base mold from Bullseye Glass forms a cut sheet of fusible glass into a shallow square dish with a flat bottom. The outer mold dimensions are 6.1 inches by 6.1 inches, with a depth of 1.1 inches; these measurements are used to check kiln fit. Because each mold is handmade by Creative Ceramics in Europe, sizes vary slightly from piece to piece, so measure your specific mold before cutting your glass blank.
A pre-cut glass blank is placed over or set into the prepared mold and heated in the kiln until the glass softens and drops into the square form by gravity. The flat-base design gives the finished dish a stable, even bottom. The mold is slipcast from a specially formulated clay body that produces an exceptionally smooth forming surface, accepts kiln wash uniformly, and does not crack under repeated proper use. It is COE agnostic, so the same mold works with COE90, COE96, or any other fusible glass; match your firing schedule and anneal soak to the glass you are using.
What does the Square Slumper B with Flat Base mold make?
How do I size my glass blank for this mold?
What COE glass can I use?
How do I prep the mold before slumping? Hotline Primo Primer or a shelf primer and let it dry fully before placing the glass blank. The mold accepts kiln wash uniformly. Re-coat as needed between firings.
Specifications
SKU: 3665Manufacturer: Bullseye Glass (made by Creative Ceramics in Europe)Bullseye design number: #8996 (item number 008996; store code BG8996)Shape: square with flat baseOuter mold dimensions: 6.1 x 6.1 x 1.1 in (16 x 16 x 3 cm)Note on sizing: molds are handmade and vary slightly; measure before cutting glassMaterial: slipcast ceramic, 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 shelf primer such as ZYP Boron Nitride Mold Primer and let it dry completely before placing your glass blank so the finished piece releases cleanly.
The outer dimensions are 6.1 by 6.1 inches, but because each mold is handmade, sizes vary slightly. Measure your specific mold before cutting your glass. Cut a test piece from inexpensive glass first when the result matters.
Place the glass blank over or into the prepared mold. Fire on a slumping schedule suited to your glass and mold depth, and visually confirm the slump during firing. Adjust the peak temperature if the glass has not fully formed or shows signs of over-slumping.
The mold is COE agnostic. Adjust the anneal soak for your glass: about 900 F for COE90, about 950 F for COE96.
Let the kiln cool fully before removing the slumped piece. Re-coat the mold with kiln wash as needed between firings.
Bullseye Suggested Slumping Schedule
This is a suggested starting schedule for slumping 6mm pieces in a Paragon GL24, 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.
Segment Rate Temp (F) Hold 1 (slump) 300 F/hr 1200 :10 2 (anneal soak) AFAP 900 1:00 3 (anneal cool) 100 F/hr 700 none 4 (natural cool) AFAP 70 none
AFAP means as fast as possible. Segment 2 is the anneal soak at 900 F, suited to COE90; adjust to 950 F for COE96. Segment 4 is a natural cool: leave the door closed and let the kiln drop to room temperature on its own.
Helpful downloads: Suggested Slumping Schedules from Bullseye Glass (PDF)
Description updated: July 6, 2026
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