How to cure polyester resin

Written by jenny harrington Google
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Polyester casting resin is used in many craft projects including jewellery and model-making. A type of plastic, resin is liquid until it cures. After curing, or drying, the resin turns into a hard plastic that is clear. Dyes may also be added to the resin to tint it varying colours or to make it opaque. Resin is mixed with a catalyst which speeds up the curing time so that most pieces are ready to use within 48 hours of casting.

Skill level:

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Things you need

  • Polyester resin
  • Catalyst
  • Measuring tools
  • Mold
  • Box

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  1. 1

    Mix the resin with the catalyst in a disposable plastic cup or bowl. Follow package instructions for exact amounts, as these differ between resin brands. Too little or too much catalyst causes resin to cure poorly or become sticky.

  2. 2

    Pour the mixed resin into a prepared resin mould. Use silicone moulds or those developed specifically for resin casting.

  3. 3

    Blow lightly on the surface of the resin to pop any air bubbles that rise to the surface after pouring. Allow the resin to sit for 5 minutes, then blow on it a second time to pop the rest of the bubbles.

  4. 4

    Cover the mould with an upside-down box to prevent dust from collecting on the surface while it cures. Set in a room with a temperature of 21.1 to 26.6 degrees C to cure for 48 hours.

  5. 5

    Remove the box after 48 hours and lightly touch the surface of the resin. If it feels hard, it is cured. If it is soft or if fingerprints are left in it, allow it to cure for an extra day. High humidity may cause resin to cure more slowly.

  6. 6

    Turn the moulds upside down once the resin is cured. Tap them lightly until the finished resin pieces pop out.

Tips and warnings

  • The surface on the open side of the mould may remain slightly sticky. Spray this with a resin spray, available at craft stores, to seal.
  • Work in a well-ventilated room and cover all work surfaces. Resin is not removable once cured.

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