How to make silicone molds at home

What you need

A master (the object you want to copy), platinum-cure or tin-cure silicone, a mold box, mold release, mixing cups, a scale, and a stir stick. Platinum silicone is best for food, resin and long life; tin-cure is cheaper and more forgiving.

Step by step

1. Clean the master and fix it to the base of the mold box so it can't float.
2. Leave at least 10 mm of space between the master and every wall of the box.
3. Spray a thin coat of mold release on the box (and the master, if it is porous).
4. Weigh part A and part B exactly by the ratio on the label — most silicones fail from guessed ratios.
5. Mix slowly for 2–3 minutes, scraping the sides and bottom.
6. Degas in a vacuum chamber if you have one, or pour from high up in a thin stream to break bubbles.
7. Pour into the lowest corner and let the silicone rise over the master.
8. Wait the full cure time on the label (often 4–24 hours), then demold.

One-part vs two-part silicone molds

A one-part (open) mold works when the object has a flat back. Anything round or with undercuts needs a two-part mold: pour the first half, add keys, apply release, then pour the second half so the halves line up.

Skip the mold box

Sirpam 3D Labs Mold builds a printable pour box, two-part block or skin + mother mold around your 3D model, with keys, pour hole and vents already placed. Print it, pour silicone, done.