One Mold, Many Props: Silicone & Resin

Casting guide 🫗 · Workshop crew · Nov 2026

Why casting is the best-dollars-per-prop trick

Gems, sigils, badge emblems, gemstones, horns — anything you need twice or more pays for a mold. Sculpt once, cast in resin, and every future costume reuses it: cast a dozen gemstones and they match forever, which sculpting never does.

The master: sculpt to survive demolding

• Clay, foam or resin-sculpted masters all work — seal porous surfaces (clay needs a sealer spray or it sticks).
• No deep undercuts on a first mold: sloped walls and open shapes release cleanly.
• Mount the master in a small box (cardboard + hot glue) with the detail side up — the pour side needs the smoothest face.

The silicone pour

1. Tin-cure RTV silicone is the beginner material: two parts, ~10:1 mix by weight, stirred slow and steady.
2. Release agent on the master (petroleum jelly thinned or a spray wax) unless the silicone is designed not to stick.
3. Pour in a thin, high stream — the fall pops most surface bubbles.
4. Cure per the data sheet, typically 4–24 h at room temperature. Warm rooms cure faster; don't rush with high heat.

Safety: cure-time fumes want ventilation, gloves always — the chemistry is mild but the mess is permanent.

Casting the prop

Pour low and slow into the deepest point, let it flow up. Cure times run minutes to hours — demold early-test a corner trim.

Bubbles and other fixes