◆ Concrete
Heirloom concrete pumpkin mold
A squat heirloom pumpkin, 150 mm across with deep lobes, to cast in concrete. A silicone mold kit from printed parts.
◆ Concrete
A squat heirloom pumpkin, 150 mm across with deep lobes, to cast in concrete. A silicone mold kit from printed parts.
A squat heirloom pumpkin 150 mm across and 75 mm tall, the flat Cinderella shape (Rouge vif d'Etampes) florists and home stores sell every fall: ten deep, rounded lobes, a wide sunken crown and a short, stout stem 22 mm thick. The lobed foot is about 95 mm across, so it sits low and steady as a centrepiece, on a stack of books or at the end of a porch step.
Made with the hugging-shell mode of our silicone mold maker. The site's mold advisor ranks a silicone box first for such a low, wide shape, but the round box would take 2.15 litres of silicone; the shell follows the lobes about 10 mm out and takes about 934 ml, which is the difference between an expensive mold and a sensible one. Print the base with the pumpkin fused onto it, the two shell halves and the six clamps, and pour.
In concrete it weighs about 1910 g, a real doorstop of a pumpkin; Jesmonite makes a lighter one. Leave it raw grey, lime-wash it chalky white, or paint it a muted blue-grey like a Jarrahdale. The zip carries every printed part, the pumpkin 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.
Print the base, which has the pumpkin master already fused onto it, the two shell halves and the six clamps (all six are in clamps.stl). No supports.
Stand the two shell halves on the base round the master, seated on the rim of the base, and push the six clamps over the seams. Steel binder clips work too, the seats for them are built into the shell.
Tape the outside seams or run a bead of hot glue along them, because silicone finds every gap.
Mix 996 ml of silicone in one batch and pour it into the open top of the shell in a thin stream until it is level with the rim, so it rises round the lobes and over the stem.
Once it has cured, take the clamps off and slide each shell half off SIDEWAYS, not upward: the pumpkin is wider above its foot, so the base rib is left open for that. The silicone skin is open only at the foot, which is narrower than the pumpkin, so cut ONE slit with a sharp knife along a crease, from the foot to about two thirds of the way up, peel the skin open and lift the master out. In a crease the seam line hides.
Put the skin back in the shell halves with the clamps on, and stand the shell upside down on the flat top of the silicone: the shell holds the slit shut and keeps the skin round, and the open foot is now on top.
Mix a fine concrete or Jesmonite to a thick pour. Brush a thin first coat into the stem and the creases, fill slowly down one side, vibrate the shell for a full minute to raise the air, and strike the foot flat.
Leave it two days, take the shell off, open the slit and peel the skin back from the foot toward the stem. Let the pumpkin cure for a week, sand the foot flat, add felt pads, and paint or seal it.
Print details
| Cast material | Concrete |
|---|---|
| Printed parts | 9 |
| Size (W x D x H) | 186 x 190 x 89 mm |
| Print bed needed | 190 x 179 mm, 89 mm tall |
| Filament | ~851 g |
| Layer height | 0.2 mm |
| Infill | 15% |
| Supports | Not needed |
| Download | ZIP: 9 printed parts in 4 STL files + pumpkin master (STL) + print sheet + recipe |
| Added | 2026-09-26 |
Pro early access until October 26, 2026, then free with any account.
Like it or post your print on Thingiverse
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.
About 1910 g in ordinary concrete, from a 868 ml cast: a solid, weighty centrepiece. For a lighter one, cast it in Jesmonite, or in a lightweight craft concrete with perlite, which comes out at roughly two thirds of the weight and still takes paint well.
Brush a thin first coat of the mix into the creases and the stem through the open foot, then fill the rest slowly down one side and vibrate the shell for a full minute. The creases are rounded, so the mix flows into them; a pinhole that stays is usually on the underside of a lobe, where a smear of the same mix fills it after demolding.
Once it has dried for a few days, brush on a thin wash of white chalk paint or lime paint thinned with water, let it sit for a minute, then wipe the lobes with a damp cloth so the grey shows through on the high points and the white stays in the creases. Seal it with a matte sealer afterwards.
ConcretePro early access
A low-poly geometric planter, 110 mm across and 90 mm tall, to cast in concrete. A silicone mold kit from printed parts.
ConcretePro early access
The classic 8 x 6 cm sphere planter to cast in concrete, with a drainage hole. A silicone mold kit from printed parts.
ConcretePro early access
A hexagon planter, 90 mm across the flats, to cast in concrete with even 8 mm walls. A silicone mold kit from printed parts.
ConcretePro early access
A tapered square planter, 95 mm at the rim and 88 mm tall, to cast in concrete. A silicone mold kit from printed parts.
ConcretePro early access
A 120 mm succulent bowl to cast in concrete, with a rounded rim and a drainage hole. A silicone mold kit from printed parts.
ConcretePro early access
A ring-stack planter, 85 mm tall with five soft ripples, to cast in concrete. A silicone mold kit from printed parts.
ConcretePro early access
A straight concrete candle jar, 80 mm across, for the classic 8 oz candle. A silicone mold kit from printed parts.
ConcretePro early access
A ribbed concrete candle vessel, 92 mm across with 30 rounded ribs. A silicone mold kit from printed parts.