How does curing work?

A UV/LED gel contains monomers, oligomers, and photoinitiators. Before curing, the material is liquid, semi-liquid, or paste-like. When exposed to the lamp’s light, the photoinitiators absorb this energy and trigger a polymerization reaction.

This reaction gradually transforms the material into a solid, durable network. This process is what allows the gel to harden, adhere properly, and reach its final strength.

Successful curing therefore does not depend only on the time spent under the lamp. It also depends on the gel formulation, the lamp’s actual output, the emitted wavelength, the condition of the LEDs, the applied thickness, and the position of the hand in the lamp.

Wavelength: a point not to overlook

A UV/LED lamp emits light in a specific area of the spectrum, expressed in nanometers — for example 365 nm, 385 nm, 395 nm, or 405 nm.

The photoinitiators in gels do not all react to the same wavelength. If the lamp does not emit in the right range, or if its intensity is too low, curing may be insufficient.

Due to changes made to photoinitiators in TPO-free formulas, effective emission around the 385–395 nm range has become essential for certain formulas.

Wattage alone isn’t enough

Many people still choose their lamp only by looking at the number of watts. This is a common mistake.

The stated wattage alone does not guarantee good curing. A poorly designed or aging 54W lamp can be less effective than a well-designed lamp with more even light output.

What really matters:

• the wavelength emitted by the LEDs
• the light intensity actually received by the nail
• LED distribution inside the unit
• the presence of a reflective base or suitable bottom plate
• the distance between the nails and the LEDs
• the overall condition of the lamp
• following the recommended curing time

The risks of poor curing

Poor curing is not always immediately visible. The gel may appear hard on the surface, while the material is not fully polymerized deeper down.

This is why it’s important not to shorten curing times, even when the product feels hard after a few seconds.

Product thickness matters too

The thicker a gel layer is, the more the light must penetrate the material. A thin layer of gel polish cures more easily than an apex, a build, or a thicker reinforcement.

Dark, highly pigmented colors, whites, blacks, or glitter gels may also require special attention. Pigments can limit light penetration, making it even more important to follow curing times.

For technical products, it is recommended to work at a reasonable thickness and follow the recommendations indicated on the product sheet.

Why are some lamps no longer enough?

With older formulas, some entry-level lamps could deliver an acceptable result. With new TPO-free formulations, this is not always the case anymore.

A lamp can be an issue if:

• it is too old or has lost intensity
• it doesn’t have enough well-distributed LEDs
• it doesn’t properly cover thumbs
• it doesn’t have a reflective base
• it isn’t suited to the photoinitiators in modern gels

Mini portable lamps can be handy for nail art or a repair, but they don’t always replace a true professional lamp for curing a full set.

Sensitive mode and heat

Curing can generate a sensation of heat. This reaction is normal: when the gel polymerizes, it releases energy. The thicker the layer, the more the reaction can be felt.

Some lamps have a sensitive mode (low heat mode) that gradually increases power. This mode is particularly useful for:

• builder gels and reinforcements
• sensitive clients
• thin or weakened nails
• sets where the material is applied thicker

Warning: sensitive mode should not be used to reduce the total curing time. It is meant to improve comfort, not to speed up hardening.

How to use your UV/LED lamp properly?

• Place the hand flat inside the lamp
• Avoid fingers touching the sides
• Pay attention to the thumb, often poorly positioned
• Follow the time indicated on the product
• Do not cure layers that are too thick if the product isn’t designed for it
• Regularly clean the base and the inside of the lamp
• Replace a lamp that is too old or unstable
• Use a professional lamp for full sets