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Photo by Lexa One

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Casting Clear Polyester Resin

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Casting resin looks intimidating when you’ve never done it, but it’s actually an easy process. With it you can create many things that are very useful for anime and game costumes such as clear jewels of any shape and size. As long as you have the appropriate mold for it, you can make any shape you want. You can get molds for resin at craft stores, on Etsy or make your own with silicone.

Supplies

  • Clear polyester resin and polyester catalyst
  • Resin dye (optional)
  • Digital weight scale
  • Disposable cup
  • Popsicle stick
  • Mold
  • Mold release spray (optional)
  • Aluminum foil (optional)
  • Glue (optional)

Let’s get started!

Polyester resin is a stinky mess so it’s better to do this whole process outside and to protect your work surface. If you decide to do that inside, make sure it’s in a well ventilated area because the fumes are toxic.

Whatever you pour resin in isn’t going to be washable so that’s why I always use disposable cups from the dollar store. Same goes for your mixing sticks! You’ll end up throwing all that away after each use.

Start by pouring enough resin in a disposable cup. It’s important to be precise, so a digital weight scale is the best thing to use. Follow the instructions that come with the resin and add the necessary amount of catalyst. If you want to colour your resin, now’s the time to add the dye. Dyes made specifically for resin exist, but it’s impossible for me to find in stores here so instead I use Pebeo Vitrail which is a type of glass paint. I suppose you could use other brands of glass paint, but I’ve never tried them so I can’t vouch for the result.

Stir very well and pour into your mold. You can spray some mold release before pouring in the resin, but this is optional. This product is self-explanatory; it makes unmolding a bit easier and also makes your mold last longer. Once the resin is poured in the mold, tap it on a hard surface to get rid of any air bubbles. If you see bubbles on the surface, use a needle to make them disappear.

When the resin hardens, it generates heat so it’s necessary to use molds that are heat resistant so they won’t melt and make a mess. To be safe, make sure you use molds that are made for resin or silicone molds (the blue mold in some of the pictures is silicone).

In general, I try to wait 12 to 24 hours before unmolding. Curing time depends on the size of your piece and the ambient temperature. The warmer it is, the faster the resin will harden. Always wait until the surface is hard before unmolding even if it’s been 24 hours.

It’s always best to use molds that are smooth and even, but in case the surface of your resin piece has imperfections, you can easily sand them down by hand starting with a coarse grit sand paper and finishing with a very fine one to smooth things down. If you do that however, it’s extremely important to wear a dust mask with the appropriate filters because resin dust is toxic. Resin that has been sanded turns cloudy white, so if you’re going for the clear jewel look you may want to add a coat of clear varnish on top.

For an opaque finish, you can use spray paint to colour your resin piece. An example of this would be the gold rings on my Margaret cosplay. For a clear and extra shiny finish, you can glue aluminium foil on the back of the piece.