Getting a glossy finish on polyester resin castings

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    • #7354
      Katherine Swift

      This question comes from Matt:

      I was making an Iceberg sculpture, the iceberg would appear to be submerged halfway in water (polyester resin). I needed a large mold so I did something that, I know now, should not have and used a paper bowl mold. The result was an incredibly matte finish and not the clear water-like result I had hoped for. My question is: Can I cut the polyester resin? It’s a thick circular block, about 2-3 inches thick and maybe 5-6 inches wide. The top of the resin that was exposed is clear!- so nothing went wrong with my curing. But I feel, and this is where your expertise would come in, if I trim the matte edges off I’ll be left with what wasn’t exposed to the paper texture that incurred the matte finish. And recommendations? Should I not do it? Should I use a specific method of cutting?

    • #7355
      Katherine Swift

      Hi Matt, in this case, I would not cut the resin. The matte finish is only on the surface of the resin, so a little surface finishing is all that should be necessary to get it shiny again.

      Polyester resin does well with a buffing wheel and compound. I have a large cabinet that I use with a cotton wheel and Fabulustre compound. You could use a smaller wheel on a flex shaft or dremel tool, but it’s going to take you awhile. Depending on how frosted your surface is, this may or may not work by itself to remove the matte surface.

      Otherwise, you may have to sand the surface first with some wet/dry sandpaper. Start with a 400 to 600 grit, then work your way down to a 1500 grit or higher sandpaper. You can then apply the polishing compound with a buffing wheel and should get a shiny finish.

    • #7356

      Ok! I actually finished this is the time between sending the question and now. I used a miter saw to trim the edges because I cast the polyester in a large, I think 5-6″ diameter flat bottom paper bowl. The result was a matte finish because the polyester adhered to the non-crystal clear texture of paper. I decided to cut the circle down to a square with a miter saw and sanded the edges from 60 grit to 2000 grit then used floor polish to clean the sides and these were the results!

      My project itself is to make an Iceberg that appears to be floating in water and I’m pretty happy with the results. Tis is my first time using resin of any kind.

      Link to picture ^^^

    • #7357
      Katherine Swift

      Looks like you still need to finish the edges by sanding. Have you tried that yet?

    • #7359
      Matthew Akos

      No, I sanded a whole bunch. If you’re talking about the fogginess that’s the camera flash. the lines are from the towel I used to polish it- I don’t have a wheel. I’m happy with it though, the project is done.

    • #7361
      Katherine Swift

      Wonderful! Glad to hear it turned out well for you.

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