The Science of Gels

What’s really going on when your client puts her hand in the nail lamp? We explain what gel is made of and why it works so well.

The word “gel” lends itself to confusion ­because it originally described the nail product’s physical state, but over the years it has become a generic name of the product category. Whereas liquid-and-powder nails are a two-part system in which the powder has already been polymerized to its full ­extent, gel is a homogenous product in which the monomers and oligomers (strings of monomers) stay in a semi-liquid/semi-solid state because it hasn’t polymerized. Think of gel as premixed acrylic.

Gel nails first appeared in the U.S. in the early 1980s, but were met with limited success. At the time, the manufacturers of gel lights and the gel itself had not joined forces, not yet recognizing the need to precisely match the intensity of the light to the photoinitiators in the gel. Nail techs and clients soon found out that ­using the wrong light or applying too much gel caused a burning sensation on the client’s fingertips. ­Additionally, education on gel application was limited, leaving nail techs in the dark about the product, and home-use ­systems were introduced around the same time, damaging the reputation of salon-use systems by ­association. By the end of the ‘80s, many companies had pulled their gel products from the market.

But by the end of the ‘90s, gel nails were back on the U.S. nail scene, now with much-improved formulas that were ­designed to work with a precise light wavelength and intensity. These new formulations also delivered better clarity and ­durability. By 2010, 63% of salons offered gel nail services to their clients, according to NAILS 2010-2011 Big Book, and gels are one of the most frequently added services to salon menus. Additional innovations in gels appeared in the 2000s, ­including 3-D gels, soak-off gels, and polish-gel hybrids (see “Innovations in Gels” below).

All in the Family

Acrylics are a special family of monomers and/or oligomers and/or polymers used to create nail enhancement products, including UV gel nails and acrylic (liquid-and-powder) nails. (Wraps and tip adhesives are in the acrylics family too, in the cyanoacrylates category.)



Cure with a free radical reaction (when the peroxide in the powder is exposed to the reactive monomer in the liquid)

Cure with a free radical reaction (when the photoinitiator in the resin reacts with the wavelengths emmited by the lamp)

Strong odor, caused by the volatile
compounds in the liquid and powder

Very faint odor, generally caused by either low vapor pressure or lack of VOCs (volatile organic compounds)


Innovations in Gels

Hybrid brush-on gel polishes are the trendiest innovation in the nail industry in recent memory. Hybrids incorporate the same types of solvents as nail polish, which allows them to soak off faster than the current group of soak-off gels in potted jars, plus the hybrids have other ingredients to lower the viscosity so that application is more similar to that of a polish, explains industry scientist Doug Schoon. Brush-on gel polishes pull ingredients from both polish and gel formulas, making them true hybrids.

Jim McConnell, president of Light Elegance, also offers his insight: “Nail polish is mostly comprised of nitrocellulose resins and solvent. Nitrocellulose resins are not known for scratch resistance while urethanes [gels] have excellent scratch resistance. You can think of UV gel polishes as nail polish taken to the next degree.”

Regarding traditional gels versus soak-off potted gels, McConnell explains that traditional gels are more cross-linked, which gives them more resistance to acetone. Soak-off gels have been altered so they can be attacked by acetone.

Gels — The Basics

GELS: pre-mixed semi-solid monomers and oligomers that are hardened to polymers when exposed to UV-A light.

Energy curable resins:
a semisolid oligomer with at least one acrylic functional group that cures via light energy.

Photoinitiators: ingredients that absorb light and convert it into the energy needed to drive the polymerization process.

Stabilizers: chemicals that are added to prevent discoloration.

Inhibitors: ingredients that prevent the gel from prematurely hardening or pre-polymerizing while still in its original container.

Pigments (optional):
insoluble, finely ground substances that impart color. Certain pigments (like white pigments) reflect some of the light that is used to cure the gels, while others (like black pigments) absorb some of UV light, and some just don’t cure well at all (many pigments fall under this category). It takes significant research to determine which pigments should be used for UV nail gel.

Non-energy curable resins (optional): functional fillers added to modify the properties of the gel, such as thickening or toughening the product.

Solvents (optional): substances in which other substances are dissolved. Brush-on gel polishes tend to incorporate an increased amount of solvents to help them break down faster than traditional soak-offs.

a light, generally containing multiple bulbs, that emits light in the correct spectrum to activate the photoinitiator in the gel. Most gels contain photoinitiators that react in light wavelengths of 340 to 380 nanometers (nm.).

Lamp (bulb) intensity: intensity refers to how much light is available for curing. Some people mistakenly think wattage is synonymous with intensity but it’s not — wattage is irrelevant to the science behind gels and simply refers to how much electricity the bulb uses.

Number of lamps: gel lights generally house from one to five lamps; three or four lamps is most common.

Light unit size:
how close the lamps are from the fingernails makes a huge difference in a light’s ability to cure gel. In general, every time you double the distance between you and a light source, the intensity drops by 75%. (That’s why flashbulbs on cameras don’t help if the subject is far away.) A gel nail held one inch from a UV lamp receives three times more light energy than one held two inches away. (This is also why occasionally looking at a gel nail light from several feet away for brief periods poses virtually no risk to your or your clients’ eyes.)

Next page: UV v. LED and Bulb Change Schedule

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