◆ Crayons

Building brick crayon mold

Twelve toy brick crayons with studs, in 2x2, 2x3 and 2x4 sizes. Melted from broken crayons in the oven.

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3D render of the printed caster for a twelve-cavity building brick crayon mold, with six blue toy brick crayons with round studs in 2x2, 2x3 and 2x4 sizes in front
Crayons ~159 g Pro early access

A silicone tray for twelve building brick crayons: four each of a 2x2, a 2x3 and a 2x4 brick on a 12 mm stud grid, 24 mm wide and 17 mm tall with the round studs on top. The set of three takes about 39 ml of melted crayon, and the chunky bricks stand on end on a desk.

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Made with our tray mold generator in its flexible silicone tray mode: print the caster, pour a heat-proof platinum silicone into it and peel out the tray. The studs form in pockets in the silicone floor, and the tray flexes off them; the printed caster never goes in the oven.

Brick crayons are a birthday party staple for kids who build: one colour per brick, or a rainbow row. They are crayons shaped like bricks, not building toys, so they do not snap onto anything. The zip carries the printed caster exactly as the tool exported it, the set of three bricks on its own as an STL, the master uploaded to the tool, and a print and pour sheet with the silicone figure the tool measured.

Shown as a 3D render of the printed caster with two sets of blue brick crayons in front, not a photo.

What you need

3
  • About 354 ml of platinum silicone rated for 200 C (400 F) or more
  • Broken wax crayons, peeled, about 39 ml of pieces per set of three
  • A baking sheet and oven mitts

How to cast it

6

  1. Print the caster as exported, open side up, no supports. It never goes in the oven: PLA softens at about 60 C.

  2. Pour 354 ml of a platinum silicone rated for 200 C (400 F) or more into one corner in a thin stream, letting it rise over the shapes to the rim. Tap out the bubbles, let it cure and peel it out: that silicone is the crayon mold.

  3. Soak old crayons in warm water for ten minutes, peel off the paper and break them into pieces about 1 cm long. Sort them by colour, or mix colours for swirled crayons.

  4. Set the silicone tray on a baking sheet. Drop small pieces into the stud pockets first, then fill each brick to the top and heap it a little: the pieces shrink as they melt, and the studs are the deepest part.

  5. Bake at 230 to 275 F (110 to 135 C) for 10 to 20 minutes, until every piece has melted. Hotter makes the wax separate into a white film on top.

  6. An adult lifts the sheet out. Let the crayons cool for 30 minutes, give the tray 10 minutes in the freezer, then flex it and pop them out. Keep this tray for crafts, never food.

Print details

5 h 20 minPrint time
~159 gFilament
1Printed parts
137 × 133 × 30 mmSize (W x D x H)
All print details
Print details
Cast materialCrayons
Printed parts1
Size (W x D x H)137 x 133 x 30 mm
Print bed needed138 x 133 mm, 30 mm tall
Filament~159 g
Layer height0.2 mm
Infill15%
SupportsNot needed
DownloadZIP: printed caster (STL) + one set of three brick crayons (STL) + tool master (STL) + print and pour sheet
Added2026-09-26

Pro early access until October 26, 2026, then free with any account.

Make your own tray mold →

Made with the free Tray mold 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 ice cube tray mold guide.

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Questions about this design

Why are the studs on my brick crayons hollow or missing?

Air stayed in the stud pockets, the deepest part of the mold. Drop small crayon pieces into each pocket before you fill the brick, and give the tray a gentle shake on the baking sheet once the wax is liquid, which lets the trapped bubbles rise out.

Do the brick crayons stack onto real building bricks?

No, and they are not meant to. The studs are rounded and 7.2 mm across on a 12 mm grid, chunkier than any toy system, so the crayons sit side by side but never clutch. That keeps small hands from forcing them together and snapping them.

How do I make a rainbow set of brick crayons?

Sort the peeled pieces into red, orange, yellow, green, blue and purple and fill each row of the tray with one colour. Twelve bricks give two full rainbows, one of each size, which packs neatly into a clear bag as a party favour.

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