Short answer: thin layers of UV resin typically cure in about 1–4 minutes under a UV/LED lamp, and roughly 5–15 minutes in direct sunlight. Times vary a lot by brand, lamp power and color, so use these as starting points and follow your resin label.
| Setup | Typical time per thin layer |
|---|---|
| UV/LED nail-style lamp (≈36–48 W) | 1–4 min |
| Small UV flashlight | 1–3 min held close |
| Direct summer sun | 5–15 min |
| Cloudy day / indoor window | much longer, often incomplete |
UV light only reaches so deep. Many brands recommend layers of only a few millimeters or less; pigments, mica and opaque colors block light and need thinner layers and longer exposure. For thick castings (coasters, trays, deep molds), two-part epoxy is the better choice.
Most craft UV resins cure in the 365–405 nm range. Check the lamp and resin both list compatible wavelengths.
A thin tacky film on the surface is common, caused by oxygen. Cure a few minutes longer, flip the piece and cure the back, or wipe the film off with isopropyl alcohol. A weak or mismatched lamp and layers that are too thick also cause it.
Yes, in direct sunlight, but it is slower and less consistent. Indoor light usually will not cure it fully.
Generally just a few millimeters per layer; build thicker pieces in layers and cure each one. Follow your brand's maximum.
It can yellow with long UV/sun exposure or heavy over-curing, like many resins. See our resin yellowing guide.
Related: resin yellowing · UV resin vs epoxy · resin for jewelry molds
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