◆ Soap

Classic rectangle soap bar tray mold

Four classic rectangular soap bars with a thin engraved frame, poured into a printed tray.

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3D render of a printed tray with four rectangular soap bar cavities, with three cream soap bars with an engraved frame beside it
Soap ~180 g

A printed tray for four classic rectangular soap bars, each 84 x 56 mm and 26 mm tall, the size of a bar cut from a soap maker's loaf. The edges are rounded to 6 mm so the bar sits well in the hand, and a thin frame is engraved 6 mm in from the edge of the face, which gives a plain bar a finished, handmade look.

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Made with our tray mold generator in its rigid tray mode: print the tray and pour melt-and-pour soap straight in, no silicone needed. The sides are drafted, so a chilled bar drops out of the rigid tray whole.

A plain bar is the one every soap range needs: it takes any colour, swirl or embed, and a stamp or label on the back. The zip carries the tray exactly as the tool exported it, one bar on its own as an STL, the master uploaded to the tool, and a print and pour sheet with the volume of each cavity.

Shown as a 3D render of the printed tray with three soap bars, not a photo.

Classic rectangle soap bar tray mold at a glance: every printed part with its size, print time, filament, print settings and the three steps to use it

What you need

3
  • A PETG print of the tray
  • Melt-and-pour soap base, about 122 ml per bar
  • Colour, fragrance and rubbing alcohol in a spray bottle

How to cast it

4

  1. Print the tray as exported, cavities up, no supports. PETG is best: melt-and-pour soap goes in at about 60 C, which is where PLA starts to soften.

  2. Melt the soap base, stir in colour and fragrance, and pour each cavity to the brim. Spray the surface with rubbing alcohol to pop the bubbles.

  3. Let the soap harden for an hour or two, then give the tray 15 minutes in the freezer so the bars shrink away from the walls.

  4. Turn the tray over and press on the back of each cavity to pop the soaps out. Wrap them once they are at room temperature, or they sweat.

Print details

6 hPrint time
~180 gFilament
1Printed parts
192 × 136 × 32 mmSize (W x D x H)
All print details
Print details
Cast materialSoap
Printed parts1
Size (W x D x H)192 x 136 x 32 mm
Print bed needed192 x 136 mm, 33 mm tall
Filament~180 g
Layer height0.2 mm
Infill15%
SupportsNot needed
DownloadZIP: printed tray (STL) + one soap (STL) + tool master (STL) + print and pour sheet
Added2026-09-30
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.

Download free on Thingiverse

Free download. Opens the Thingiverse listing in a new tab.

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

How much does one rectangle soap bar weigh?

Each bar holds about 122 ml, so a melt-and-pour bar comes out at roughly 125 g, a standard size to sell. A 1 kg block of base fills the tray twice with a little to spare.

Can I pour cold process soap into the printed tray?

You can, but lye soap stays in the mold for a day or two and is caustic until it has cured, so keep the tray for soap only and demold with gloves. Melt-and-pour is easier: it sets in an hour and drops out after 15 minutes in the freezer.

How do I stop bubbles on the face of the soap bar?

Spray the empty cavity with rubbing alcohol, pour at the low end of your base's temperature range, and spray the top again straight after pouring. The face of the bar is the bottom of the cavity, so the alcohol in the cavity is what keeps the engraved frame crisp.

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