How to Apply PVA to a Mold

Mirrored car wax is used to prep molds for PVA application.

Polyvinyl alcohol, or PVA, is a water-based plastic used to prevent castings from sticking to waxed molds. While PVA can be applied to a mold with a brush or roller, PVA is typically found already packaged in aerosol cans. Therefore, spraying PVA is the most common route. PVA is used on many types of molds, including silicone, fiberglass, plastic and plaster. Automotive-style wax is used to seal the surface before the PVA is applied.

Things You'll Need

• Mold
• Wax
• Lint-free cloth
• PVA

Instructions

1. Apply high-quality wax with a mirrored finish to the mold. Use a lint-free cloth and rub the wax into the mold until well covered.

2. Apply two more coats in the same manner.

3. Hold the PVA can 12 to 18 inches from the surface of the mold, and hold down the nozzle. Mist the entire surface of the mold with a light coat. Allow it to dry for 15 minutes. Repeat.

4. Spray on a heavier coat of the PVA. This is often called a flow coat because you should be able to see the PVA flowing slightly on the mold. Allow it to dry for 30 to 45 minutes and repeat for one to two more coats.

5. Allow the mold to dry for at least an hour after the final PVA coat before casting.

References

• US Composites: Product Bulletin - PVA
• West System: Mold Release - PVA and Hairspray
• Winship Models: PVA Mold Release