How to Sand Fresh Cured Polyester Resin

There are two different types of polyester resin. One is called a laminating or bonding resin. This type of resin cures with a slightly tacky surface and should not be sanded unless it is specially cured in an air-tight environment. The other type of polyester resin is known as marine or fiberglass resin. This resin dries with a hard, waxy finish and can be sanded before finishing.

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Things You'll Need

  • Resin applicator
  • 120-grit sandpaper
  • 180-grit sandpaper
  • Tack cloth
  • Clean your surface well and then mix and apply marine or fiberglass polyester resin as per the manufacturer's instructions. Shape the resin close to the final shape you desire.

  • Cure the resin for a minimum of six hours at room temperature. Feel the surface of the resin. If it feels smooth and slick to the touch, then it is properly cured -- if it feels tacky or sticky, then allow it more time to cure.

  • Sand the surface of the cured resin with 120-grit sandpaper. Do not sand heavily. Sand to remove any fibers or other imperfections. Shape as you sand.

  • Sand with 180-grit paper for the final sanding to smooth the surface of your resin until it is virtually as smooth as glass. Wipe the sanding resin down with a tack cloth and then paint if desired.

Tips & Warnings

  • Always use fresh resin, purchased no more than six months previously.
  • Do not use more catalyst when mixing resin than the manufacturer suggests.
  • Mix small quantities of resin at a time, as the resin begins setting up within 15 to 17 minutes.


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