Halloween Pumpkin Candle From a 3D-Printed Two-Part Mold (No CAD Needed)

Halloween is around the corner, and I wanted a candle that would actually look like a carved jack-o'-lantern — grinning face, ribbed sides, the whole thing. Store-bought pumpkin candles are usually smooth and boring, so I decided to make my own.

The trick is a rigid two-part mold printed in plain PLA. No silicone, no expensive materials: you print two halves with a pumpkin-shaped cavity inside, band them together, pour wax through a hole in the top and open the mold a few hours later. When the candle burns down a little, the face starts to glow from the inside.

You can design a mold like this in any CAD program if you're willing to spend some time on it. Personally, I used 3DGEN - it builds the mold from any STL in a few seconds, right in the browser, with no CAD skills needed.

For the mold:

- A 3D printer and PLA filament - PLA handled the hot wax with no problems

- A pumpkin STL - I used "Pumpkin for Clicker and Twisty tutorial" by Sentinel Peak Design Studio (CC0, public domain) from MakerWorld: https://makerworld.com/en/models/3111758

For the candle:

- Soy wax - I added a little paraffin to it

- Candle dye - any wax colorant of your choice

- A waxed candle wick with a metal tab

- Double-sided tape or wick stickers, plus a small piece of regular tape

- 2 rubber bands

- A pouring pitcher or small pot, a double boiler to melt the wax, and a spoon to stir

- Petroleum jelly (Vaseline) as a release agent

How much wax? This pumpkin is 88 × 88 × 66 mm and needs about 278 ml / 250 g. Melt noticeably more than that: the wax shrinks as it cools and you'll need to top it up, and a second batch melted later rarely matches the color of the first.

Open the mold generator and upload the pumpkin STL. The model appears on a virtual print bed with a plane through it - that plane is where the mold will split into two halves.

The one rule I followed: the pumpkin's face has to sit entirely in one half. If the split line runs across the eyes and mouth, you get a seam right through the face. Keep the face in one half and it comes out crisp. For this pumpkin a vertical split through the middle does exactly that, and nothing locks the wax in. If you need a different angle, the Rotate X/Y/Z sliders turn the split plane.

I kept all settings at their defaults:

- Model size: 100%

- Pour hole: 9 mm

- Wall thickness: 5 mm

- Half-to-half seal: Tongue & groove (it seals liquids better than pins)

Click "Build cavity" and the two halves appear a few seconds later. Pull the "Explode halves" slider to look inside and check the cavity, then download the STL (or 3MF).

Print both halves in PLA.

I printed them side by side in one go with a 0.2 mm layer height and 10% infill

It took about 15 hours.

Coat the inside of both cavities with a thin layer of petroleum jelly. It keeps the wax from sticking to the PLA and makes opening the mold much easier. I skipped it on this pumpkin and regretted it.

Press the halves together - the tongue-and-groove seam lines them up. Then put two rubber bands around the mold. The mold has channels for them, so the bands sit flat and don't slip.

Stick the metal tab of the wick to a small piece of double-sided tape and drop the wick through the pour hole so the tab sits at the bottom of the cavity.

Pull the wick straight up so it stands vertically in the center, and fix the top end to the mold with a small piece of tape. That keeps it straight while you pour.

Melt all your wax in one batch, add the dye, and heat it to the pour temperature recommended for your wax. Pour slowly through the pour hole until the cavity is full.

Wax shrinks as it cools: after 10-15 minutes the level drops noticeably and a dip forms around the wick. Top it up from the same batch - keep the leftover warm for this.

This is where I made a mistake: I didn't melt enough, ran short, and had to melt a second batch for the top-up. It came out a different shade, and the top of my pumpkin around the stem ended up lighter and yellower than the rest. One batch with extra wax avoids this.

Leave the mold alone for 30 minutes at room temperature, then put it in the fridge for 2 hours.

Cooling makes the wax shrink slightly away from the walls, which helps it release.

Take off the rubber bands and pull the halves apart.

Honestly, this was the hardest part for me - without a release agent the wax held on to the PLA, and I had to work it out carefully. Two lessons:

1. Don't skip the release agent. Petroleum jelly is enough. For comparison, a candle cast in a silicone mold came out much more easily.

2. Avoid undercuts. If the model widens or has overhangs relative to the split line, the wax gets locked in and won't come out. Pick a split where each half "opens" freely.

Take the pumpkin out and trim the wick. There will be a thin seam line where the halves met. I left mine as is, but you can clean it up with a knife, a hair dryer or just your fingers if you want a perfectly smooth candle.

Then turn off the lights and light it. Once the candle burns down a little, the carved face starts to glow from the inside.

A few final notes:

- The mold is reusable - you can cast a whole row of pumpkins for the porch or the table.

- Melt more wax than you think you need and pour from a single batch.

- Use a release agent and avoid undercuts.

- The same method works with any STL: skulls, ghosts, little bats.

- Pumpkin model: "Pumpkin for Clicker and Twisty tutorial" by Sentinel Peak Design Studio, CC0 (public domain).

What should I cast next? Drop your ideas in the comments - I'd love to try them.

Happy Halloween!