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Opal brooch with cuttlebone casting

Cuttlebone casting Step 5
Need to learn cuttlebone casting? Check out this step-by-step tutorial by Jennifer Stenhouse.


  • Sterling silver: scrap or casting shot
  • Sterling silver sheet: 20-gauge (0.8mm), half-hard, 1 in. (25.5mm) 
  • Sterling silver wire: 18-gauge (1.0mm), round, half-hard, 4 in. (10.2cm)
  • Fine-silver or gold bezel wire: 3 in. (76mm)
  • Sterling silver pin-back findings: hinge, catch, stem
  • Boulder opal: free-form cabochon 
  • Small, faceted gemstone
  • Cuttlefish bones
  • Jeweler’s saw; spiral and 2/0 blades 
  • Wire cutters
  • Belt sander (optional)
  • Dust mask
  • Safety glasses
  • Sandpaper: 220 grit 
  • Soft-lead pencil: B 
  • Soft, broad paintbrush
  • Carving tool: clay tool, dental tool, or craft knife
  • Soft, nonstick clay 
  • Pumice pan 
  • Ceramic crucible with handle
  • Iron binding wire 
  • Soldering station: Torch, solder (hard, medium, and easy), fire-resistant work surface (soldering pad, firebrick, or charcoal block) pickle pot with pickle, flux, steel tweezers (cross-locking and precision), copper tongs, solder pick 
  • Powered borax flux
  • Carbon stirring rod
  • Brass brush
  • Jeweler’s files: needle, hand
  • Pliers: chainnose, flatnose
  • Flex shaft, rubber abrasive disks, mandrels
  • Burnisher
  • Masking tape (optional) 
  • Polishing cloth


Opal brooch with cuttlebone casting Step 1
Step 1
Make the bezel cup. After casting a one-sided design in the cuttlebone, shape the casting with files and sandpaper.
Opal brooch with cuttlebone casting Step 2
Step 2
Create a bezel-cup setting for an opal. Place the bezel cup in position against the casting in preparation for soldering.
Opal brooch with cuttlebone casting Step 3
Step 3
Make a two-prong head. Use flatnose pliers with 18-gauge (1.0mm) sterling silver round wire to form an under-bezel for a faceted gemstone. The under-bezel is a lip of metal, which should fit snugly under the gemstone’s girdle to support the gemstone in a mounting. Cut two 1⁄4-in. (6.5mm) prongs for the head from 18-gauge (1.0mm) sterling silver round wire. Push them into the soldering block to hold them in place against the under-bezel. The under-bezel and prongs will form a two-prong head. Position themon the side of the casting. 

Use a soldering pick to solder the bezel cup, the under-bezel, and the two prongs to the casting with medium solder. Pickle, rinse, and clean the piece with a brass brush and soapy water.
Opal brooch with cuttlebone casting Step 4
Step 4
Attach the findings. Sweat easy solder on the bottom of the pin-stem hinge and catch. Flux the back of the brooch, and heat the entire piece gently. Place the pin-stem hinge and catch on the back of the brooch with tweezers, making sure that the findings are lined up so that the pin stem will align with the catch. The hinge should be at the top of the brooch and the catch at the bottom. Pin-back findings are placed this way so gravity will help to keep the brooch in place if the pin catch comes open during wear. Continue to heat until the solder flows; promptly remove the heat to avoid melting the findings. Pickle the brooch, then rinse and clean it with a brass brush and soapy water. 

Pre-polish the brooch. Clean up any excess solder or prong wire with files, sandpaper, or rubber abrasive disks on a flex-shaft mandrel. Complete all polishing before setting the stones or installing the pin stem.
Opal brooch with cuttlebone casting Step 5
Step 5
Set the stones. Use a burnisher to gently roll the edge of the bezel over the side of the opal until the gemstone is set firmly in place. To set the faceted gemstone, use a triangular needle file to make a small groove in each prong above the under-bezel where the gemstone’s girdle will hit the prong. Place the gemstone on the under-bezel, and push the prongs down onto the gemstone. Trim any extra prong from the top of the gemstone with wire cutters and files. Be especially careful when setting opals and faceted gemstones — they are easily scratched. Some craftspeople protect their gemstones by covering them with masking tape during setting.
Opal brooch with cuttlebone casting Step 6
Step 6
Attach the pin stem. Put the rivet pins in place in the pin-stem hinge, and squeeze the hinge closed with a pair of pliers.
Opal brooch with cuttlebone casting Step 7
Step 7
Clip the pin stem so that the end of the pin reaches 1mm (1⁄32 in.) past the catch. File the end of the pin stem to a smooth, tapered point. Polish and finish the brooch with a soft polishing cloth.

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