How to make wax melt & crayon molds

To make wax melt or crayon molds, design a multi-cavity tray — a grid of identical little shapes — print it, then pour melted wax in and pop the pieces out once they've set. The one thing to get right is heat: hot wax can soften a PLA print, so print a rigid tray in a heat-tolerant filament, or use the tray as a master to cast a silicone mold for the hottest pours. Here's the full process with the casting tray generator.

What you're making

Wax melts (the scented cubes for wax warmers) and recycled crayons are both small, repeated shapes poured from melted wax — exactly what a casting tray is for. The casting tray generator takes any shape you upload and lays it out as a grid of identical cavities. It works in two modes:

• Rigid tray — print the tray and pour wax straight into it, then pop the pieces out.
• Silicone-pour mold — print a master inside a trough, pour silicone around it, and use the flexible silicone tray for casting.

Step 1 — Pick a shape and build the grid

1. Upload your shape as an STL — a heart, star, cube, letter or logo. Simple, chunky shapes release best.
2. Set Model size so each piece is the size you want (wax melts are usually bite-sized cubes or shapes; crayons are often chunky for small hands).
3. Choose Columns and Rows for how many pieces per pour, and the Gap between cells.
4. Set the Outer wall and Floor thickness — a sturdier tray resists flexing when it's full of hot wax.
5. In Rigid mode, use the Seam position to choose how much of the shape becomes the cavity — keep it where the shape stops widening, so the piece has a way out (see draft & undercuts).

Step 2 — Choose rigid or silicone (the heat question)

This decides whether your tray survives. Common pour temperatures are roughly 54–66 °C for soy wax, 68–74 °C for beeswax and 71–82 °C for paraffin (check your wax supplier's numbers). Standard PLA starts to soften around 60 °C, so:

• Rigid tray in PETG or ASA — these tolerate more heat than PLA and suit lower-temperature wax melts poured at the cooler end of the range. Let the wax cool a little before pouring.
• Silicone tray (recommended for paraffin and crayons) — switch to Silicone-pour mode, print the master (PLA is fine here, it never touches hot wax), pour silicone, and cast into the silicone. It handles heat well and flexes to release pieces easily.

For the full filament comparison, see best filament for 3D printed molds.

Step 3 — Pour and release

• Melt wax gently in a double boiler or a dedicated melting pot, and add fragrance or colour per the wax maker's guidance.
• Pour steadily into each cavity to just below the rim; tap the tray to release bubbles.
• Let it set fully at room temperature. A short spell in the fridge can help pieces shrink slightly and pop out.
• Release: flex a silicone tray from underneath; for a rigid tray, press each piece out from the back — a light release agent helps (see the mold release guide).

Making crayons from old crayons

Crayons are mostly paraffin wax, so treat them like a hot pour. Peel off the paper, break them into pieces, and sort by colour. Many people melt the pieces inside the mold in a low oven — if you do that, the mold must be heat-safe silicone; a printed plastic tray should never go in the oven. Alternatively, melt the pieces in a double boiler and pour into a silicone tray. Hot wax burns: an adult should handle the melting and pouring.

FAQ

Can I pour wax into a PLA print?

It's risky. PLA softens around 60 °C, and many waxes are poured hotter than that, so the tray can warp. Print in PETG or ASA, or cast a silicone tray from a printed master.

Why won't my wax melts come out?

Usually straight-sided or undercut cavities. Choose simpler shapes, place the seam where the shape stops widening, chill the tray briefly, or use a flexible silicone tray.

Can I use the same tray for soap or chocolate?

The generator supports those pours too, but keep trays used for wax and fragrance separate from anything you'll use with food. For soap, see soap molds.