The Square Slumper 6 inch Sushi from Colour de Verre is a reusable ceramic slumping form designed to shape pre-fused glass into the silhouette of a classic square sushi plate. The form stands about 2 inches high and measures about 6.5 inches square, sized to fit inside an 8-inch kiln with clearance between the form sides and the kiln walls.
Three practical design details set this slumper apart from other slumping forms. The closed bottom lets you set the form on kiln posts, which improves heat circulation underneath and around it during firing. The low profile keeps it clear of pyrometer sensors in small, front-loading jewelry kilns. And its compact overall footprint is sized to leave enough space between the form sides and the kiln walls when working in an 8-inch kiln.
Like all ceramic slumping forms, this one is COE agnostic. Place a pre-fused blank on the form, fire to a slump temperature suited to your glass and kiln, and the glass settles into the square plate shape. The form is reusable across many firings when prepped and cared for properly.
What does the Square Slumper 6 inch Sushi make?
It shapes pre-fused glass into a square sushi plate silhouette, about 6 inches across, in a single slump firing.
What glass can I use with this form?
Any COE. Ceramic slumping forms are COE agnostic, so the same form works with COE96, COE90, or other fusible glass. Match your firing schedule to the glass you are using.
Why does the closed bottom matter?
A closed bottom lets you elevate the form on kiln posts so heat circulates underneath it as well as around the sides. This helps the form and glass heat more evenly during firing.
Will this form fit in a small kiln?
Yes. The form is about 6.5 inches square and about 2 inches high, sized to fit inside an 8-inch kiln with space between the form sides and the kiln walls. The low profile also keeps it clear of pyrometer sensors in small front-loading kilns.
Specifications
- SKU: 182329
- Manufacturer: Colour de Verre
- Makes: one square sushi plate shape per firing
- Finished piece size: about 6 inches square
- Form size: about 6.5 inches square x about 2 inches high
- Fits in: 8-inch kiln (with clearance from kiln walls)
- Material: ceramic slumping form, reusable
- Glass: any COE (COE agnostic)
Working Notes
These are guidelines, not guarantees. Every kiln fires a little differently, so test a small run first when the result matters and follow the Colour de Verre project sheet for this mold.
- Prime the form surface with ZYP Boron Nitride Mold Primer or Hotline Primo Primer before every use, and let it dry completely before placing glass on the form.
- Set the form on kiln posts to take advantage of the closed bottom design, which allows heat to circulate underneath the form.
- Place a pre-fused blank centered on the form. Fire to a slump temperature suited to your glass and kiln.
- The form is COE agnostic. Use a slump schedule matched to your glass, and adjust the anneal soak temperature for your COE.
- Let the kiln cool fully before removing the slumped piece. Prime the form again before each subsequent firing.
Colour de Verre Suggested Firing Guidelines
This is a suggested starting point, not a guarantee. Every kiln fires differently. Follow the Colour de Verre project sheet for this mold and test a small run first before committing to a production firing.
- Heat no faster than about 350 F (195 C) per hour to avoid thermal shock to the form and glass.
- Fire to a slump temperature suited to your glass and kiln, keeping the peak temperature to no more than about 1450 F (785 C).
- Add a brief hold at peak temperature, then cool in a controlled way to an anneal soak. A standard anneal soak is about 900 F for COE90 glass or about 950 F for COE96 glass.
- Cool slowly through the annealing range before allowing the kiln to return to room temperature.
Helpful downloads: Priming Molds With ZYP Spray (PDF)
Description updated: July 6, 2026
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