How to Prep and Prime Resin Miniatures — Stop Paint Flaking

Nothing is more frustrating than spending hours painting a figure, only to have the paint flake off when you touch it. The problem is almost always inadequate prep. Resin is not plastic — it needs different treatment. Here's the process that guarantees paint adhesion.

Why Resin Needs Special Prep

Resin kits are cast in silicone moulds. To release the cured resin, manufacturers use a mould release agent — a waxy, oily substance that coats every surface. This release agent is invisible, but it actively repels paint. Skip the cleaning step and your paint will bead up, dry poorly, and flake off within days.

Step 1: Wash Thoroughly

Fill a bowl with warm (not hot) water and add a generous squirt of dish soap — the degreasing kind works best. Submerge all parts and scrub each one with an old toothbrush, paying special attention to recesses and undercuts where release agent pools. Rinse under running water and repeat. Two washes is the minimum; three is better.

Step 2: Soak (Optional but Recommended)

For extra insurance, soak parts in warm soapy water for 30-60 minutes after scrubbing. Some builders use isopropyl alcohol (IPA) as a final rinse — this dissolves any remaining residue. Let parts dry completely before moving on. A hairdryer on low speed this up.

Step 3: Remove Mould Lines

Once clean and dry, remove all mould lines and flash with a sharp hobby knife. Sand any rough areas with 400-600 grit sandpaper. For curved surfaces, wrap sandpaper around a dowel or brush handle. Check every part under a bright light — mould lines that look minor now will scream at you after priming.

Step 4: Pin Large Parts

For joints that bear weight (arms, heads, weapons on vehicles), drill matching holes with a pin vise and insert brass rod. This creates a mechanical bond that super glue alone can't match. Use 0.5mm wire for small figures, 1mm for larger pieces.

Step 5: Prime

This is the critical step. Use a primer specifically designed for resin or multi-surface use:

• Spray primers: Tamiya Fine Surface Primer, Citadel Chaos Black/Grey Seer, Mr. Surfacer 1500
• Airbrush primers: Vallejo Surface Primer, Badger Stynylrez
• Brush-on primers: Vallejo Brush-On Primer (thin coats only)

Apply in thin, even coats. Two light passes are better than one heavy one. Let each coat dry fully (30-60 minutes for spray, longer for brush-on). The primer coat should be smooth and uniform — if you can still see resin colour showing through, add another light coat.

Step 6: Inspect Under Light

After priming, examine the model under a bright directional light. Primer reveals every imperfection — scratches, air bubbles, remaining mould lines. Fix any issues now by sanding, filling with putty, and re-priming the affected area. It's much easier to fix problems at this stage than after painting.

Common Mistakes to Avoid

• Skipping the wash: The #1 cause of paint adhesion failure on resin
• Using plastic cement: Plastic cement dissolves polystyrene — resin isn't polystyrene. Use super glue (cyanoacrylate) only
• Thick primer coats: Heavy primer fills in fine detail. Always use multiple thin coats
• Priming in humidity: High humidity causes primer to dry with a fuzzy, rough texture. Prime in dry conditions or use an airbrush indoors

Get the prep right and your paint will bond permanently. Skip it and nothing else matters — no amount of painting skill compensates for poor adhesion.

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