Sanding and Polishing Resin Jewelry to a Glass Finish

A clean pour from a quality glossy mold doesn’t need sanding. The finish comes straight off the mold — smooth, reflective, done. But if your piece has scratches, a rough seam, dull spots, or you’ve drilled holes and the entry points need cleanup, sanding is how you fix it.

The process is straightforward but order matters. Skip grits, rush to the polish, and you’ll still have scratches — just finer ones.

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When you actually need to sand

Not every piece does. Before you start, check what the problem actually is:

Dull finish from a matte mold: Matte molds intentionally produce a frosted finish. Sanding won’t make it glossy until you work through all the grits and polish. That’s the process below — takes 10–15 minutes per piece.

Scratches from handling: Light scratches from contact with other pieces or tools. Start at 800 if they’re fine, 600 or 400 if they’re deep.

Flash or mold seams: Thin ridges of resin along the mold parting line. Sand at 220–400 to remove the high point, then work up through the grits.

Rough edge from drilling: A burr or rough ring around a drilled hole. A few passes with 400, then smooth the edge with 800.

Cloudy or frosted overall: If the whole piece is cloudy from a mixing or curing issue, sanding and polishing can sometimes improve the surface clarity, but it won’t fix cloudiness that’s internal to the resin. That’s a different problem.

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The grit sequence

Sandpaper grits to keep on hand: 400, 600, 800, 1000, 1500, 2000. Wet/dry sandpaper (silicon carbide, black) is what you want — designed for use with water, cuts cleanly without clogging.

The starting grit depends on how much material you need to remove:
– Heavy scratches, seams, or rough areas: start at 400
– Light surface scratches: start at 800
– Just dulling the finish for polishing: start at 1500

Wet sand. Keep the sandpaper and the piece wet — dip both in water before each pass. Wet sanding cuts faster, stays cooler, keeps the sandpaper from loading up with resin dust, and produces a finer result than dry sanding.

Work each grit until the scratches from the previous grit are gone. You’ll be able to see when — the surface should show only the current grit’s marks, evenly distributed. Miss a grit and the deeper scratches will still show through the polish at the end.

A full sequence from 400 through 2000 on a small pendant takes 10–15 minutes total. The individual grit steps are only 2–3 minutes each when you’re working with purpose.

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Polishing

After 2000 grit the surface will look uniformly matte — smooth but not glossy. Polishing compound is what brings the shine back.

Plastic polish: Novus Plastic Polish No. 2 (for light scratches) or the full Novus 3-step system. Available at hardware stores and Amazon. Apply with a soft cloth in circular motions, buff to a shine. This is my standard choice.

Automotive polish: Meguiar’s PlastX or Mothers Mag & Aluminum Polish. Works as well as Novus. Any plastic-safe compound will do — avoid abrasive car polish meant for clear coat, which is too aggressive.

Polishing by hand: Apply a pea-sized amount to a soft cloth (microfiber works well). Work in small circles over the piece. It’ll look worse before it looks better — the polishing compound makes a slight haze initially. Keep going; it clears as you buff.

Rotary tool polishing: A cloth polishing wheel on a Dremel with a bit of compound cuts the time to under a minute for small pieces. Run slow (5,000–10,000 RPM), use light pressure — too much heat from the tool and you’ll soften the resin surface.

After polishing, clean the piece with a soft damp cloth to remove compound residue.

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Interior surfaces (rings, concave pieces)

The inside of a ring or a bowl-shaped piece can’t be reached with flat sandpaper. Options:

• Small foam sanding sticks (sold for nail care — these are the exact right shape)
• A wooden dowel wrapped tightly in sandpaper
• A conical Dremel sanding drum for rotary finishing

Work the same grit sequence — just with a curved or shaped tool instead of a flat sheet.

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What to expect from the result

A well-sanded and polished piece should be indistinguishable from a piece that came out of a high-quality glossy mold — smooth, reflective, no scratches visible under normal light.

The realistic limitation: if the piece has internal cloudiness or bubbles below the surface, polishing the exterior won’t fix those. Sanding and polishing is a surface treatment, not a cure for deep resin problems.

For most jewelry pieces, a clean pour means minimal finishing. I sand maybe 20% of what I make — usually pieces where the mold seam is more prominent than usual, or where I drilled and need to clean up the drill point. The rest comes out ready to wear.

Browse bmmold.com molds for jewelry.

What’s the issue with the piece you’re trying to fix? If you describe the finish problem, I can tell you where in the grit sequence to start.

— Nikolai