Big Skull Mold

The Big Skull Mold from Colour de Verre casts one glass skull measuring 4.5 inches (11.5 cm) long in a single firing. The mold body is 6.5 inches long by 5 inches wide and 2 inches deep, giving the cavity enough volume for 300 grams of glass. Fill it with frit, 6mm sheet glass cuttings, or billet chunks and fire to cast a solid skull form. Once the initial cast is complete, a second firing with laminated dichroic sheet glass laid over the piece can add depth and vivid color.

Like all ceramic casting molds, this one is COE agnostic. The same mold works with COE96, COE90, or any other fusible glass. Colour de Verre molds require priming with a boron nitride separator before every use. With proper prep and care, the mold is reusable across many firings.

What does the Big Skull Mold make?
It casts one skull measuring 4.5 inches (11.5 cm) long per firing. The 2-inch-deep cavity produces a solid, substantial form well suited to display pieces and sculptural glass work.

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

How much glass do I need?
Colour de Verre lists 300 grams as the fill weight for this mold. Frit, 6mm sheet cuttings, and billet chunks all work. Weigh your glass and test a first run when the result matters.

Can I add dichroic glass for a second effect?
Yes. Colour de Verre notes that a second firing with laminated dichroic sheet glass laid over the cast skull can add vivid color and depth. Complete and fully anneal the initial cast first, then plan the dichroic firing as a separate step.

How do I prep the mold before use?
Prime all surfaces with a boron nitride separator before every firing. Let the primer dry completely before adding glass so the finished piece releases cleanly.

Specifications

• SKU: 182005
• Manufacturer: Colour de Verre
• Makes: 1 skull per firing
• Finished piece size: 4.5 inches (11.5 cm) long
• Mold size: 6.5 inches L x 5 inches W x 2 inches deep (16.5 x 13 x 5 cm)
• Fill weight: 300 grams
• Fill materials: frit, 6mm sheet cuttings, or billet chunks
• Material: ceramic kiln casting mold, 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 mold before every use. Colour de Verre recommends ZYP Boron Nitride Mold Primer or Hotline Primo Primer. Apply a full coat and let it dry completely before loading glass into the cavity.
• Fill the cavity with frit, 6mm sheet glass cuttings, or billet chunks. Colour de Verre lists 300 grams as the fill weight. Billet chunks tend to produce especially clear cast results.
• The mold is COE agnostic. Use a full fuse casting schedule matched to your glass.
• Heat no faster than about 350 F (195 C) per hour to protect the ceramic mold and avoid thermal shock in a thick glass load.
• Fire to no more than about 1450 F (785 C). Exceeding this temperature can damage the mold.
• Include an anneal soak matched to your glass: about 950 F for COE96, or about 900 F for COE90. Use a controlled cool through the anneal range.
• Let the kiln cool to room temperature before removing the cast piece. Re-prime the mold before each subsequent firing.
• For a second dichroic firing, complete and anneal the skull cast fully first, then lay the laminated dichroic sheet over the finished piece and fire as a separate session.

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 large or irreplaceable glass load.

• Ramp no faster than about 350 F (195 C) per hour through the heating phase.
• Target a top temperature of no more than about 1450 F (785 C).
• Hold at top temperature as needed for the glass to fully flow into the cavity, then begin a controlled cool.
• Anneal soak: about 950 F for COE96, or about 900 F for COE90.
• Let the kiln cool fully to room temperature before opening and removing the cast piece.

Helpful downloads: Priming with ZYP Spray (PDF) · Tricks of the Trade (PDF)

Description updated: July 6, 2026

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