System

Crushed Stone Casting System

Cast it yourself — natural crushed stone set in gypsum for pieces with real mineral depth.

Coverage 1 m² per 5 kg

Cure Time Cures in 24–48 h

Skill Level Beginner-friendly

Specifications, explained

The numbers that decide how a cast behaves — and what to watch for at each step.

Base High-strength gypsum: Harder than pottery plaster, so thin walls survive demoulding without chipping.
Aggregate Natural granite grit, 1–3 mm: Grain size decides how coarse the surface feels — 1–3 mm suits trays, discs and coasters.
Mix ratio Gypsum : water = 100 : 35 by weight: Too much water costs strength and leaves a chalky surface. Weigh it, do not eyeball it.
Batch yield 500 g gypsum → one 20 cm disc: Size the batch to the piece you are casting, so nothing sets in the bowl.

Working time 8–10 minutes after mixing: Past that the mix thickens and stops flowing into fine detail.
Demould 15–20 minutes — surface no longer tacky: Too early and the edges slump; too late and the piece fights the mould.
Full cure 24–48 hours: Strength keeps climbing for two days — do not load or wet the piece before then.
Sealing Once fully dry, dip in the polyurethane sealer for 20–30 s, then air-dry: The dipped coat cures into a glossy protective layer.

Thickness 12–15 mm: Thick enough to feel solid in the hand without a long cure.
Surface Matte · P2500 (2000-grit) edges · PU sealed: Sealing locks the grit in and stops oil and water marks soaking in.
Water resistance Water-resistant once the film dries: Once the sealed surface dries into a cured film, it offers a degree of water resistance.
Room temperature 18–25 °C ideal: Below 10 °C curing slows sharply and the surface stays soft for days.