◆ Plaster

Plaster fluted corbel mold

A fluted block corbel, 110 mm tall, with a stepped top and three flutes down a cove. Cast it in plaster.

3D render of the fluted block corbel master fused on its printed charcoal base, between the orange and blue shell halves, with the charcoal clamps behind
Plaster ~284 g Pro early access

A plain, classic block corbel 110 mm tall, 62 mm deep and 52 mm wide: a two-step top plate, a quarter-round cove sweeping down to a narrow foot, and three flutes running down the cove. It suits a simpler room than the scroll corbel, and it is small enough for a floating shelf, a window head or a picture ledge.

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Made with the hugging-shell mode of our silicone mold maker, which takes about 250 ml of silicone for this corbel where a square box would take 712 ml. Print the base with the corbel fused onto it on its back, the two shell halves and the clamps, pour the silicone, and cast through the open back.

Cast in casting plaster, Hydrocal or Jesmonite and paint it the colour of the wall or leave it white. The zip carries every printed part, the corbel master as its own STL, the tool's own print-settings sheet and a recipe file for the generator.

Shown as a 3D render of the printed mold parts pulled apart around the master, not a photo.

What you need

4
  • About 278 ml of silicone (mix it in one batch)
  • Casting plaster, Hydrocal or Jesmonite: each cast is 179 ml
  • Tape or a hot glue gun for the shell seams
  • Construction adhesive or a screw and wall plug to mount it

How to cast it

7
  1. Print the base, which has the corbel master already fused onto it on its back, the two shell halves and the clamps (all of them are in clamps.stl). No supports.

  2. Stand the shell halves on the base around the master and push the printed clamps over the seams. Steel binder clips work too, the seats for them are built into the shell.

  3. Tape the outside seams or run a bead of hot glue along them, because silicone finds every gap.

  4. Mix 278 ml of silicone in one batch, pour it into the open top in a thin stream, and fill level with the rim.

  5. Once it has cured, unclip the shell, lift it off and peel the silicone off the master. That silicone is your mold.

  6. Turn the silicone over and set it back in the shell: the opening is the flat back of the corbel. Fill it with plaster, tap the shell for a minute to raise the air, and strike the back flat with a ruler.

  7. After an hour peel the silicone off. Let the corbel dry for a few days, then sand the back flat and paint or seal it.

Print details

9 h 30 minPrint time
~284 gFilament
9Printed parts
98 × 160 × 83 mmSize (W x D x H)
All print details
Print details
Cast materialPlaster
Printed parts9
Size (W x D x H)98 x 160 x 83 mm
Print bed needed160 x 96 mm, 83 mm tall
Filament~284 g
Layer height0.2 mm
Infill15%
SupportsNot needed
DownloadZIP: 9 printed parts in 4 STL files + corbel master (STL) + print sheet + recipe
Added2026-09-25

Pro early access until October 25, 2026, then free with any account.

Make your own silicone mold →

Made with the free Silicone mold maker generator. Upload your own model and get the same kind of mold built around it, in your browser.

Free for personal use. Selling the pieces you cast needs a commercial licence (Pro or Founder); passing on the file itself is not permitted on any plan. Full terms.

New to casting? Read the silicone mold maker guide.

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Questions about this design

How do I mount the plaster fluted corbel?

Glue it with construction adhesive or a plaster adhesive, and for anything that carries weight also drill a hole through from the top and screw it into a wall plug. Fill the screw head with a dab of plaster and paint over it.

Can I cast the fluted corbel in concrete?

Yes, in a fine concrete or Jesmonite for a porch or an outdoor shelf. Vibrate the mold well so the flutes fill, let it cure for a week and seal it before it goes outside. Plaster is for indoors only.

Why is the fluted corbel mold a shell, not a box?

Silicone. A square box round this corbel takes about 712 ml, the hugging shell about 250 ml for the same cast, and the flexible silicone still peels cleanly out of the flutes.