Epoxy coating is the technique that makes a 3D printed prop look injection-molded. Applied over primed PLA, epoxy fills layer lines, self-levels to a smooth surface, and cures to a hard finish that sands better than any filler primer. XTC-3D, Art Resin, and UV resins all do this, but they do it differently. Choosing the right one depends on the size of the piece, the surface quality you need, and whether you want to sand afterward.
XTC-3D: The Layer Line Eliminator
XTC-3D by Smooth-On is a two-part epoxy specifically formulated for 3D printed surfaces. It has low viscosity that allows it to flow into surface texture and self-level. Mixed 2:1 (part A to part B), it has a working time of approximately 10 minutes and reaches full cure in 2-4 hours.
Application: Apply over primed PLA with a foam brush in thin coats. The epoxy self-levels as it flows across the surface. One coat typically fills 0.2mm layer lines completely on flat surfaces. Curved surfaces may need two coats in deep concave areas where the epoxy thins as it flows away from the center.
Sanding after XTC-3D: After full cure, XTC-3D sands with standard sandpaper to an optically smooth surface. Start at 220-grit, work to 400-grit. The sanded XTC surface is the cleanest base for metallic paint finishes. No primer needed over sanded XTC-3D.
Best for: Large curved surfaces (helmet domes, large armor panels, breastplates) where layer lines need to be eliminated over a large area. The self-leveling property handles curves that filler primer and sanding struggle with.
Art Resin vs UV Resin for Cosplay
Art Resin is a two-part epoxy designed for art and craft applications. Similar to XTC-3D but formulated for clarity rather than surface filling. It produces a glass-clear finish. Good for decorative surfaces where clarity matters. Not as effective as XTC-3D at filling deep layer lines because its formulation prioritizes optical clarity over gap-filling.
UV resin is the fastest option and the only one that doesn’t require measuring and mixing. Apply, cure under UV, done in 2-3 minutes. Lower total coverage but excellent for detail areas, gems, lenses, and small accent surfaces. Can be layered: cure a base coat, apply a second coat, cure again to build up thickness.
Decision guide:
- Large surface area, eliminate layer lines: XTC-3D
- Clear decorative gloss finish on small surfaces: Art Resin
- Gems, lenses, spot gloss on details: UV resin
- Speed is the priority: UV resin