Alginate vs Silicone: Which Mold Material Should I Choose?
Quick answer (TL;DR): Use alginate for a quick, single-use lifecast (skin-safe, sets in 2 min, inexpensive). Choose platinum silicone for reusable molds with fine detail, heat resistance, and a 20+ year shelf life.
Comparison Table
| Feature | Alginate | Platinum silicone |
|---|---|---|
| Set time @ 75 °F | 2–6 min | 30–60 min (adjustable) |
| Reusability | Single-use | 50–200 pulls |
| Detail resolution | ≈ 100 µm | < 25 µm (skin texture) |
| Tear strength | Low | High (≈ 20 kN m-1) |
| Safe on skin? | Yes (food grade) | Yes (platinum cure) |
| Shrinkage | 0.5 % plus water loss | < 0.1 % |
| Material cost ($/lb) | $5–7 | $19–25 |
When to Choose Which?
- Alginate: Baby feet, quick hand casts, demo classes, single pull busts.
- Silicone: Reusable production molds, hot-wax casting, prosthetic face pieces, food-safe chocolate molds.
Recommended Products
- FiberGel™ (Slow, Med, Fast) — λ-free alginate, 3× tear strength.
- MoldRite Silicone — platinum cure, Shore A 10, skin-safe.
Written by Edmund McCormick, Mold-Making Trainer. • Last reviewed 19 June 2025