A good release agent determines success or failure in mold making. Too much, and you lose surface details. Too little, and the casting sticks in the mold. This guide compares the common release agent types and explains when each system is used.
Why release agents?
Although silicones are generally self-releasing , there are numerous situations in which a release agent is indispensable:
- Silicone on silicone: When pouring silicone over a silicone mold, the new material would otherwise permanently adhere to the existing one
- Reactive casting materials: Polyurethane resins, certain epoxides, and polyester resins adhere aggressively to silicone molds
- Extend service life: Release agent reduces wear on the mold surface
- Non-silicone molds: Molds made of GRP, wood, plaster, metal, or 3D printing always require release agents
Comparison of release agent types
| Type | Base | Release film | Detail accuracy | Suitable for |
|---|---|---|---|---|
| Wax release agents | Carnauba wax/paraffin wax | Thin, glossy | ★★★★☆ | GRP molds, resin, concrete |
| PVA Release Agent | Polyvinyl alcohol/water | Water-soluble film | ★★★☆☆ | Resin on GRP, epoxy on epoxy |
| Silicone spray | Silicone/solvent base | Ultra-thin | ★★★★★ | Fast demolding, universal |
| PTFE spray | Teflon dispersion | Dry film | ★★★★☆ | Abrasive materials, high temperature |
| Vaseline/Grease | Petroleum | Thick, oily | ★★☆☆☆ | Large molds, concrete, plaster |
| Semi-permanent | Reactive silicone | Bonded layer | ★★★★★ | Series production, 50+ demoldings |
Wax release agents
The Classic. Carnauba wax is applied thinly, dries to a hard, glossy film, and enables clean demolding. For optimal results: apply 3 to 5 coats, polishing each coat. Suitable for GRP lamination, resin casting in GRP molds, and concrete mold making.
Disadvantage: Time-consuming (multiple layers), wax residues on the casting can impair painting.
→ Renlease QZ 5111: silicone-free wax release agent for EP, PU, and polyester systems
PVA release lacquer (polyvinyl alcohol)
The Safe One. PVA release lacquer forms a water-soluble film that is simply washed off after demolding. It is often used in combination with wax : first wax as a base layer, then PVA as a safety layer.
Particularly recommended when epoxy resin is cast onto an epoxy mold : without PVA, there is a risk of permanent bonding.
Silicone spray as release agent
The Quick One. Silicone spray (e.g., ACHEM SG-1001) provides immediate release action with minimal application. Ideal for fast series and prototyping. The ultra-thin film hardly affects surface details.
Caution: Silicone spray can make subsequent painting impossible (cratering). In environments where painting is done: use silicone-free release agents .
Semi-permanent release agents
The Professional. Reactive release agents that form a permanent, bonded release layer on the mold surface. One application lasts for 20 to over 50 demoldings. Significantly more efficient than wax or spray in series production.
→ All release agents in the shop
Which release agent for which casting material?
| Casting material | In silicone mold | In epoxy/GRP mold | In metal mold |
|---|---|---|---|
| Epoxy resin | None or silicone spray | Wax + PVA | Wax or semi-permanent. |
| Polyurethane resin | Silicone spray recommended | Wax + PVA | Wax or semi-permanent. |
| Silicone on silicone | Vaseline + Dish Soap | - | - |
| Plaster / Concrete | None required | Vaseline or Wax | Oil or wax |
| Wax (Candles) | None required | Silicone spray | Silicone spray |
| Tin / Low-Melting-Point Metal | None (heat-resistant silicone) | - | Graphite or BN |
Practical Tips
- Less is more: A release agent film that is too thick fills in fine details and degrades surface quality
- Breaking in new molds: The first 2 to 3 casts of a new silicone mold often require more release agent than subsequent ones
- Silicone on Silicone: The only reliable method is a barrier layer of Vaseline mixed with a drop of dish soap (for better wetting)
- Series production: Invest in semi-permanent release agents: the time savings pay off from 20 parts
