If you are staring at three bottles labeled hard, soft, and gel and wondering which UV resin to buy, here is the short version: buy a hard type as your default, add a soft type only for pieces that need to flex, and reach for a gel (high-viscosity) type when you need the resin to build height without running off. These are not quality grades of one product — they are three formulations tuned for three different jobs, and the brand matters far less than picking the right type for what you are making.
For roughly 90% of crafters the decision is genuinely that simple. A hard type (around 85D Shore D, about 2000 cps) casts in molds, fills bezels, domes pendants, and coats flat work — all with a rigid, glass-clear finish. That single bottle covers most of what hobby jewelry and small-craft work demands. You only step outside it when a piece must bend, or when you need the resin to hold a shape while it cures. The comparison table above lays out all three side by side; the rest of this guide explains why each one behaves the way it does so you can match type to project on your own.
The 30-second answer
- Hard = your default. Rigid, glass-like, scratch-resistant. Casting, bezel fill, light doming, flat coating, sealing polymer clay.
- Soft = flex without snapping. Bendable and elastic. Open-back bracelet links, ring bands, thin charms, phone-grip accents.
- Gel / high-viscosity = build height. Thick enough to stay put on curves and verticals. Domes, 3D petals, raised lettering, waves.
And the one rule that overrides resin choice entirely: UV light only reaches about 2-4 mm deep. Every type, no exceptions, must be poured and cured in thin layers. A deep one-shot pour stays gummy at the bottom no matter which formula you bought. For anything thicker than a fingernail, layer it or switch to two-part epoxy — see our UV resin vs epoxy resin breakdown for where the line actually falls.
Hard type UV resin: the do-everything default
Hard type is the resin most people should reach for first. The headline numbers in the specs above tell the story: up to 85D Shore D hardness and around 2000 cps viscosity. That hardness is what gives cured hard resin its glassy, scratch-resistant surface — it behaves like a tiny slab of clear glass once fully cured. The 2000 cps viscosity is the clever part: it is thin enough to self-level into a smooth flat coat and flow into the corners of a bezel, yet thick enough to hold a light dome without immediately running off the edge.
That balance is why a single hard-type bottle handles so many jobs:
- Mold casting — pours into silicone molds and picks up fine detail.
- Bezel filling — flows into metal settings and self-levels to the rim.
- Light doming — builds a modest curve on flat pendants.
- Flat coating — seals paper, pressed flowers, polymer clay, and flat artwork.
Quality hard resins like the Let’s Resin Hard Type 2.0 also report under 2% cure shrinkage and cure in 3-5 minutes under a standard 36W lamp, with low odor. The budget Puduo option in the table trades published spec detail for a self-degassing formula that fights bubbles and a starter tool kit — a reasonable first bottle, though its thinner body is even worse at doming than a standard hard resin. The trade-off for all hard types is rigidity: a hard-cured piece that needs to flex will simply crack. That is the whole reason soft type exists.
Soft / flexible type: when a piece has to bend
Soft type cures to roughly 15D Shore D — and you will also see flexible variants sold around 25A on the softer Shore A scale. In plain terms, it cures bendable and elastic instead of rigid. That single property makes it the right (and only) choice for thin or wearable pieces that would snap as a hard cast:
- Open-back bracelet links that twist around the wrist
- Ring bands that flex on the finger
- Thin dangling charms that take knocks
- Phone-case and phone-grip accents that bend with the case
The Zdspoxy and Let’s Resin Soft Type entries in the table share the rest of hard resin’s profile — low, self-leveling viscosity, under 2% shrinkage, a crystal-clear yellow-resistant finish, and the same fast 3-5 minute cure. The Let’s Resin bottle even publishes a specific 15D figure, which is useful when you want predictable flex. The catch runs the opposite direction from hard type: soft resin dents and scratches easily, so it is wrong for rigid pendants or any domed showpiece, and its slightly tackier surface can attract dust before and after cure. Match it only to pieces where flexibility is the actual requirement.
Gel / high-viscosity type: building height that stays put
Gel (or high-viscosity) type is the specialist. At roughly 5000-6000 cps it is two to three times thicker than hard resin — a slow, almost paste-like flow. That thickness is the entire point: it lets the resin sit on a curved or vertical surface and hold its shape instead of running down and pooling. It still cures hard (the Let’s Resin gel reaches up to about 90D, the highest hardness in this lineup), so you get a rigid finish and dimensional shape. Use it for:
- Domes that rise well above a flat pendant
- 3D petals and sculptural flower work
- Raised lettering and relief detail
- Wave and ripple effects that a thin resin would flatten out
The downsides are the flip side of that thickness. Gel is too thick to self-level a clean flat coat, it is fiddly to work into fine bezels and small molds, and trapped bubbles rise out of it much more slowly — so plan to pop them deliberately rather than waiting for them to clear themselves.
Matching type to project
Put the three together and most decisions sort themselves out:
- Pendants, earrings, filled bezels, small mold casts: hard type.
- Open bezels, bracelet links, ring bands, thin/flexible charms, phone accents: soft type.
- Raised domes, 3D petals, lettering, waves on a flat base: gel type.
- Smooth flat coats over art or clay: hard type (self-levels); never gel.
- Anything deeper than ~4 mm: none in one pour — layer it, or use epoxy.
A common real-world combo is a hard-type flat cast or bezel finished with a gel dome on top: the hard layer gives the scratch-resistant base, the gel gives the raised, glassy crown without dripping over the edge.
The universal limit: UV cures only 2-4 mm deep
This is the fact that trips up nearly every beginner, so it is worth stating plainly: UV resin cures only about 2-4 mm deep per pass, and no resin type changes that. UV light loses energy as it travels through the resin, and below a few millimeters there simply is not enough intensity left to trigger the cure. The result is a piece that looks cured on top but stays soft, sticky, and gummy underneath.
The physics is unforgiving here — doubling your cure depth takes roughly a tenfold increase in UV intensity, which is why “just buy a stronger lamp” is not a real fix. Thin layering is mandatory. To build depth, pour and fully cure one ~2-4 mm layer, then stack the next on top. For castings deeper than a fingernail, two-part epoxy is the better tool because it cures from the inside out instead of relying on light. If you are wrestling with a soft underside, our sticky uncured resin fix guide walks through the recovery steps.
Curing gear and technique
The recommended setup is a 36W or stronger lamp at 365-405 nm wavelength. At that power, a thin layer of any of these resins cures in 3-5 minutes; in direct sunlight, budget 10-15 minutes. A few technique notes that prevent the two most common failures:
- Sticky bottom = too deep or too little light. Pour thinner, keep the piece close to the lamp, and flip or rotate it so the light reaches the underside. Extend cure time before assuming the resin is bad. The right lamp matters — see our pick in best UV lamp for resin curing.
- Tacky top = air inhibition. Oxygen interferes with the surface cure. A final cure under a cover, or curing the top under a thin film or submerged setup, gives a hard, non-tacky finish.
- Bubbles rise fastest in thin hard and soft resin; in thick gel you will need to pop them manually with a pin or a quick pass of low heat before curing.
Safety and limitations
A short, conservative safety note, because UV resin is often treated as harmless: liquid UV resin is a skin and respiratory sensitizer. Work in a ventilated space, wear nitrile gloves, and avoid skin contact — sensitization can build with repeated exposure. The fumes are real even though the cure is fast.
On durability, none of these resins is bulletproof. All UV resins can yellow over time under sun and heat, hard casts can become brittle, and soft pieces dent. And the limitation that matters most for kitchen and tableware projects: none of these consumer UV resins — hard, soft, or gel — is food-contact certified. Even fully cured, they can leach small amounts of chemicals under heat, acidic or fatty foods, or repeated washing, and uncured resin is outright toxic. Keep UV resin away from anything that touches food or drink and use a certified food-contact epoxy instead; our food-safe epoxy and FDA CFR 21 guide explains what those certifications actually require.
The bottom line
Buy a hard type first — it is the genuine all-rounder and will cover the large majority of jewelry and small-craft work. Add a soft type when, and only when, a piece must flex, and a gel type when you need to build height that would otherwise run off. Above all, respect the 2-4 mm cure-depth ceiling on every type: layer thin, cure fully, and switch to two-part epoxy for real depth. Get the type-to-job match right and UV resin stops being a guessing game.