5” Kidney Box

The 5 inch Kidney Box mold set from Colour de Verre includes two separate ceramic molds that together produce a complete kidney-shaped glass box: one mold for the base and one mold for the lid. Each piece is cast independently by filling the mold with glass and firing so the glass takes the kidney form. The result is a finished two-piece box suited for display, keepsakes, or jewelry storage.

The base mold measures approximately 7.25 by 6 by 2.25 inches and holds about 385 grams of glass. The lid mold holds about 180 grams. Both molds accept any fusible glass, since ceramic casting molds are COE agnostic. Fill each cavity with frit of any mesh, billets, casting rocks, nuggets, pebbles, sheet glass broken or cut to fit, nipped rods, or a combination of these. After both pieces are cast, a second tack fuse firing lets you add decorative Colour de Verre castings to the lid or base surface. Blossom, pine cone, leaf, dragonfly, butterfly, and scarab designs from the Colour de Verre range are noted additions.

What does this mold set make?
It casts a complete two-piece kidney-shaped glass box, with the base and lid each fired separately in their own mold. Both molds are included in the set.

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

How much glass do I need for each mold?
Colour de Verre lists about 385 grams for the base mold and about 180 grams for the lid mold. Weigh your glass before loading and test a first run when the result matters, since fill weight can vary with how you pack the cavity.

Can I decorate the finished box?
Yes. After casting both pieces, a second tack fuse firing lets you attach decorative Colour de Verre castings to the lid and base. Blossom, pine cone, leaf, dragonfly, butterfly, and scarab designs are noted as good additions.

Specifications

• SKU: 182323
• Manufacturer: Colour de Verre
• Makes: one kidney-shaped glass box (base and lid, two separate molds in the set)
• Base mold size: approximately 7.25 inches L x 6 inches W x 2.25 inches H
• Base mold fill weight: about 385 grams
• Lid mold fill weight: about 180 grams
• Material: ceramic kiln casting molds, reusable
• Glass: any COE (COE agnostic)

Working Notes

These are guidelines, not guarantees. Every kiln fires a little differently, so follow the Colour de Verre project sheet for this mold and test a small run first when the result matters.

• Prime both molds before every use. Colour de Verre recommends ZYP Boron Nitride Mold Primer or Hotline Primo Primer. Let the primer dry completely before adding glass so the cast piece releases cleanly.
• Fill each mold with frit of any mesh, billets, casting rocks, nuggets, pebbles, sheet glass broken or cut to fit, nipped rods, or a combination. Target about 385 grams for the base mold and about 180 grams for the lid mold.
• Both molds are COE agnostic. Use a fusing schedule matched to your glass and adjust the anneal soak for your COE.
• Fire each mold separately. Let the kiln cool fully before removing cast pieces. Re prime both molds before each subsequent firing.
• After both pieces are cast and annealed, a second tack fuse firing lets you attach decorative Colour de Verre castings to the lid or base surface.

Colour de Verre Suggested Firing Schedule

This is a suggested starting schedule, not a guarantee. Every kiln fires differently. Follow the Colour de Verre project sheet for this mold and test a small run first.

• Heat no faster than about 350 F (195 C) per hour
• Fire to no more than about 1450 F (785 C)
• Add a controlled cool and an anneal soak at a temperature suited to your glass: about 950 F for COE96, or about 900 F for COE90

Helpful downloads: Priming Molds With ZYP Spray (PDF)

Description updated: July 6, 2026

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