Nail decorations has been around for centuries, as far back as the ancient Egyptians and Chinese, among whom nail colors were a symbol of social status and wealth. However, ancient nail colors were based on vegetable or mineral colorants buffed into the nail; without modern polymer technology the possibilities for complex nail art were limited.
This changed in the 1920s with the introduction of modern nail lacquers. More recently there’s been a vast expansion of nail art’s popularity with the rise of social media. People use their nails to express personality, style, creativity, identity, etc. through fashion and upgrading manicure services — and then share it with the world on the internet. There are a variety of techniques and styles to choose from — dots, stripes, simple French tips, geometric patterns to intricate designs — the possibilities are endless.
As most readers already know, the nail sculpting industry began when a dentist repaired his own broken fingernail using liquid/powder dental acrylic. It may be less widely known that gel systems are also a spinoff from the dentistry field. Both systems are based on acrylate and/or methacrylate chemistry, which is very low in toxicity and why they can be used for dental fillings, dentures or even bone paste. If you get some dental work and the dentist uses blue or purple light to harden the filling, now you know that the product is very similar to the gels you use in the salon.
Gel nail technology has become an industry favorite because of its low odor, durability and the ability to cure quickly with the UV lamp. The formulations have of course diverged considerably from their dental roots. There has been a progression from old-school nail sculpting gels (which came only in a few shades) to the diverse colored “gel polish” for coloring the nail and advanced nail gels, which are better suited for nail art than their predecessors.
Chemistry of Gel
Unlike traditional lacquer, gel is not made mainly of polymers dissolved in solvent and deposited on the nail (like paint). Instead, a gel system creates polymers right on the nail. The raw ingredients of gels are (meth)acrylate monomers, (meth)acrylate oligomers and photo-initiators, as well as colorants and viscosity modifiers like those in lacquer. When the photo-initiators are activated by UV bulbs or UV/LEDs, the monomers and oligomers react, forming the polymers.
Since the monomer/oligomer mix is a viscous liquid (hence the name, gel), it can be spread on the nail without need for solvents. This greatly reduces the odor of the product, compared to conventional nail lacquer, and eliminates drying time. Secondly, and perhaps even more importantly, since it is now possible to make polymers right on the nail, there is a much broader choice of functional ingredients available. Conventional nail lacquer can only use polymers that easily dissolve in volatile solvents, but the strongest polymer coats require cross-linking (the formation of chemical bonds between different monomer chains, as illustrated in Figure 1).
Let's quickly break down gel chemistry terminology.
- Monomer: Meaning "one part" in Greek, a monomer is a molecule that can chemically react to link up with others.
- Oligomer: Greek for "of few parts," oligomers are a short chain of monomers, chemically bound to one another.
- Polymer: Greek for "many parts," polymers are a long chain or network of chemically bound monomers.
- Photo-initiator: Combining Greek “light” and Latin “beginning,” a photo-initiator is a chemical that starts a reaction when activated by certain light wavelengths.
- Solvent: Coming from Latin for “loosen, untie," a solvent is a chemical, usually a liquid, that has the ability dissolve other substances (e.g. water is a good solvent for sugar).
The greater strength of crosslinked coatings comes at the price of being harder to dissolve or soften in solvent. This is why gels can be made stronger than comparable nail lacquers – and is also why they take longer to remove. Sculpting gels are even more cross-linked than colored gels, which makes removal harder still.
Of course, the full strength of the gel does not develop unless curing is complete, and incomplete curing can not only cause service failure but skin exposure to uncured monomers and oligomers, which can result in allergic contact dermatitis. So, for full curing, and optimum client safety, it is important to:
- Use the manufacturer’s recommended curing lamp for the correct time.
- Avoid applying colored gels too thick, as the curing light only penetrates a certain depth.
- Never blend gels with colored nail lacquers; this, unfortunately, common practice is virtually certain to result in under-curing, since the gel was designed to cure only with its original color level. If the manufacturer specifies that two or more gels can be blended or swirled safely, that’s fine.
Another aspect of gel chemistry that is relevant to the nail tech is that oxygen interferes with the acrylic curing reaction at the very surface – leaving the well-known uncured residue, which is often misnamed the “dispersion layer," but is more accurately known as the “inhibition layer.” Advanced gel systems tend to have less of this, but it’s very difficult to engineer a perfectly tack-free colored gel. Again, skin exposure of uncured material is best avoided for safety reasons, so be sure to:
- Wipe off the final uncured layer with isopropyl alcohol, avoiding contact with the client’s skin or your own, or,
- Use a tack free topcoat, if you have one that works with your system.
Selecting a Gel System
Nail tech/educator Heather Reynosa has some thoughts on how to select a system that’s best for precise application and will give the best results for your clients, not to mention boosting your reputation as a nail tech when you post the beautiful result on social media. Her recommended items to look for are as follows.
- Vivid, supercharged pigmentation, for intense color coverage and full color payoff with a few coats.
- Stiff viscosity. Look for a brand that has stays put until curing, but self-levels or self-corrects just enough that it won’t leave streaky brush stroke.
- Low inhibition layer, and therefore less tendency to “slip.”
- High quality brush design, for optimum product pickup, control and flow, which gives an easier and more precise application
- Match the lamp to the gel. Each responsible manufacturer tunes their own gels to cure completely with their own lamps. There’s no such thing as a “universal” lamp.
- Made by a reputable manufacturer who applies the highest safety standards for ingredients and products. This is especially important when complicated curing chemistry is utilized to ensure that the usage and reactions are well understood and analyzed.
Good Gel Results
With the right gel, you will get the following benefits:
- Better line work: The gel will hold still until you cure it.
- Ombres: Blending is easier and less “swirly.”
- Stamping: The lower inhibition layer helps the stamping stick better instead of sliding off. It will behave more like double-stick tape than the old-school, thicker tacky layers.
- Anything you can do with traditional art paint.
Troubleshooting
Solve gel issues such as the following:
- Wrinkling: Product may be too thick to fully cure; try a thinner application.
- Lifting from cuticle: Check your nail prep.
- Lifting from the nail: Possibly user wear, or product is being applied too thick.
- Pitting: Either something was left behind on the previous layer, or you’re mixing incompatible systems. (Just don’t!)
