Pro Tips › Nails
What Is Visible Light Curing?
The Third Nail Lamp Technology Explained
- Photoinitiators
- Wavelength
- Depth of Cure
- Compatibility
Visible light curing hardens a light-cured nail coating using light in the visible spectrum, above 400 nm, rather than ultraviolet light. Traditional UV lamps and LED lamps both cure with ultraviolet light, which ends at 400 nm. A visible light lamp moves the output just past that line. The chemistry is the same in every case: a photoinitiator in the product absorbs light and starts the reaction that turns liquid gel into a solid coating. What changes is the wavelength, and a photoinitiator only responds to the wavelengths it was designed to absorb. That is why a visible light lamp is built for products formulated for it, such as the CND systems the new CND Visible Light Lamp is designed to cure.
For years the lamp conversation has had two sides, UV and LED. Our guide to UV vs LED nail lamps made the point that the names are a little misleading, because LED lamps emit ultraviolet light too. They just do it in a narrower band.
Visible light curing is the first genuinely different third option. This guide explains where it sits on the spectrum, why wavelength matters to the chemistry, and what to check before adding a visible light lamp to the desk.
The Chemistry
Every lamp does the same job
Gel and Shellac do not dry. They cure. The product contains short molecules, monomers and oligomers, plus a photoinitiator. When the photoinitiator absorbs light of the right wavelength it breaks apart and starts a chain reaction that links those short molecules into a solid polymer network.
That is true whatever lamp is on the desk. UV, LED and visible light lamps are three ways of delivering light to a photoinitiator. The only question that matters is whether the light the lamp produces is light the photoinitiator in that product can absorb.
The rule everything rests on
A photoinitiator responds to the wavelengths it was designed to absorb. Light outside that range does very little, however bright the lamp or however long the hand stays in it.
The Spectrum
Three lamps, three places on the spectrum
Ultraviolet light runs up to 400 nm. Visible light starts there, at the violet end, and runs through blue, green and red. Nail lamps sit close to that boundary, which is why the differences between them are easy to miss and still matter.
| |
Traditional UV |
LED |
Visible light |
| Light source |
Fluorescent tubes |
Light-emitting diodes |
Light-emitting diodes |
| Where the output sits |
A broad spread across the UV band |
Narrow bands in the near-UV, close to the 400 nm boundary |
Above 400 nm, in the visible spectrum |
| Ultraviolet? |
Yes |
Yes |
No, by definition, since the output is above 400 nm |
| What it cures |
Products with photoinitiators that absorb across the UV band |
Products whose photoinitiators match its narrow output |
Products whose photoinitiators absorb above 400 nm |
Not a new idea, just new to nails
Dentistry has cured tooth-coloured composite fillings with blue visible light for decades, using photoinitiators chosen to absorb in the blue. The principle a visible light nail lamp relies on is a well established one.
Depth of Cure
Why wavelength and opacity interact
Light has to travel into a coating to cure it, and not all of it gets far. Pigments, opacity and thickness all absorb and scatter light on the way through, and in general shorter wavelengths are absorbed and scattered more strongly. More of their energy is used up near the surface, and less reaches the bottom of the layer.
That is the mechanism behind a familiar problem. When the top of a layer cures before the body underneath, the surface can wrinkle as the softer material below it moves. It shows up most with highly pigmented, opaque shades and with thick or high viscosity products, which is also where thin layers matter most. Our guide to why gel polish lifts and peels covers what an incomplete cure leads to.
This is the problem CND says its visible light technology was designed around. CND states that the lamp improves curing of highly opaque light-cured nail coatings, improves depth of cure on high viscosity coatings and reduces wrinkling of CND Shellac shades. Those are CND's statements about its own product. The general principle, that wavelength affects how far light travels into a pigmented coating, is the reason the claim is worth understanding.
Compatibility
The rule cuts both ways
The photoinitiator rule that separates UV from LED applies here too. A visible light lamp cures products whose photoinitiators absorb above 400 nm. A gel formulated only for UV or LED output should not be assumed to cure under it, and a product formulated for visible light should be cured the way its manufacturer specifies.
- Read the system, not the lamp. Every professional product states the lamp and cure time it is formulated for. That instruction is the specification.
- Match the lamp to the brand. The CND Visible Light Lamp is designed for CND light cured systems. Other brands should be cured in the lamp their manufacturer specifies.
- Use the presets for the product. Cure times set for one system are not a guide to another.
- Keep the basics. Thin layers, product kept off the skin and every nail positioned in the light matter in any lamp. The UV vs LED guide explains why undercuring is a health issue as well as a wear issue.
The CND Lamp
What CND has built
The CND Visible Light Lamp is the first lamp on the Salon First range to use visible light curing. CND states that it uses diodes emitting within the visible spectrum, above 400 nm, and that it cures CND light cured systems without using UV LED light. The Salon First listing names CND Shellac, Plexigel and Brisa.
Light
Above 400 nm
Diodes in the visible spectrum, with a reflective inner shell designed to carry light around the nail, including the edges.
Power
Cordless
Rechargeable, with a charge CND rates at up to a full working day, and an LCD showing the countdown timer and battery level.
Settings
Five presets
Marked 1, 2B, 2S, 3 and IR, the last an optional red light setting. A removable baseplate makes room for pedicures.
For techs working outside the CND system, the wider gel lights and accessories range covers LED, hybrid and flash cure lamps matched to other systems.
Before You Buy
Is it the right lamp for your desk?
The decision is the same one that applies to any lamp. Start from the products you use and work back.
- You work mainly in CND. The lamp is designed for your system, so it is a direct fit. Gel polish vs Shellac covers how Shellac differs from other gel polishes.
- You run several brands. Keep a lamp that each brand specifies. One lamp will not automatically suit every system on the shelf.
- You do a lot of opaque shades or thick product. This is the situation the depth of cure question is about, so it is worth understanding what CND says its lamp is designed to address.
- You work mobile or at pedicure stations. Cordless operation and the removable baseplate are practical points in its favour.
Summary
Same chemistry, new wavelength
Visible light curing is the same photoinitiator chemistry as UV and LED curing, delivered just past the ultraviolet band. Whether a lamp cures a product still comes down to one question: does the product's photoinitiator absorb the light the lamp produces? For CND systems, CND has built a lamp around that answer. For everything else, the manufacturer's lamp specification is still the rule.
FAQ
Frequently asked questions
What is visible light curing?
Curing a light-cured nail product with light in the visible spectrum, above 400 nm, instead of ultraviolet light. A photoinitiator in the product absorbs the light and starts the reaction that turns the liquid into a solid coating, the same chemistry used by UV and LED lamps at a different wavelength.
How is a visible light lamp different from an LED lamp?
Both use diodes. An LED nail lamp emits narrow bands in the near-ultraviolet, close to the 400 nm boundary. A visible light lamp emits above 400 nm, in the visible spectrum. Each cures products whose photoinitiators absorb the light it produces.
Does a visible light lamp use UV?
Ultraviolet light ends at 400 nm, so light above that is not UV by definition. CND states that its Visible Light Lamp uses diodes emitting above 400 nm and cures CND light cured systems without using UV LED light. Curing fully and keeping product off the skin still matter whichever lamp is used.
Can I use any gel polish in a visible light lamp?
Not automatically. A product cures only if its photoinitiator absorbs the light the lamp emits. The CND Visible Light Lamp is designed for CND light cured systems. For other brands, use the lamp and cure time their manufacturer specifies.
Which products does the CND Visible Light Lamp cure?
CND describes it as designed for all CND light cured systems, and the Salon First listing names CND Shellac, Plexigel and Brisa.
Why does wavelength affect depth of cure?
Light is absorbed and scattered as it travels into a coating, and pigments, opacity and thickness all add to that. In general, shorter wavelengths are absorbed and scattered more strongly, so less of their energy reaches the bottom of a thick or opaque layer.
Why does gel polish wrinkle under the lamp?
Wrinkling usually means the surface cured before the material underneath it, often in a thick layer or a highly pigmented shade. Thin layers, the correct lamp for the product and the manufacturer's cure time are the first things to check.
Trade Account
Match the lamp to the system
Salon First stocks the CND Visible Light Lamp alongside the full gel lights and accessories range, gel colour polish and base, top and prep, with wholesale pricing for registered salon professionals. Working in CND? Browse the CND range.