I got my nails done for my convocation ceremony. My friends and I were greeted with a number of options: basic, shellac, acrylic… not to mention the selection of colours we had to choose from as well. But the quest for a perfect manicure has far preceded last Wednesday afternoon.
History of Nail Polish
The adornment of nails dates as far back as 3000 B.C. as a mark of wealth, power, and class in China. A base composition of beeswax, gelatin, and egg white was complemented by pigments from flowers or metals to give the fingernails a wash of colour. Originally, gold and silver marked royalty, later red and black were also viewed as such. These same dark colours were popular in Egypt, India, and Africa where individuals with higher capital would stain their nails using henna. Fast forward to 18th-century Europe where powders would be buffed against nails to leave a coloured stain.
Modern nail polish is much more complex. As I learned at the nail salon, there are a number of formulas used today. Unsure of what our options meant, I went with shellac and my friend got basic polish. As we waited for each layer to dry, my hands were placed under a light, his under a fan. My curiosity as to why thus sparked this article.
It all starts with basic liquid polish being applied in layers to the nail. In 1911, Cutex began a line of nail care products including cuticle removers, nail tints, and eventually a liquid polish. Unlike beauty trends today, it took some time for the popularity of these products to take off. In 1920, the invention of an acetone-based remover drove product sales and other companies followed suit. Revlon, another household brand, developed a nail enamel that mimicked the glossy finish of car paints. The next leap was surprisingly from the field of dentistry. In 1957, dentist Frederick Slack created a false nail form using dental acrylic and aluminum foil, which was the origin of acrylic nails. With time, the typical formulation of the basic nail polish was adopted by more and more cosmetic brands. In the 1980s, Essie expanded their colour options, including “ballet slippers” and “mint candy apple” that are tried and true classics to this day.
Chemistry of Nail Polish
The most common nail polish applications are basic, gel, and shellac. All of which serve the same baseline function: to add some colour, shine, or design to our fingertips.
Basic polish is what you probably picture when you think of doing your nails; a bottle of lacquer that is applied in thin coats and left to air dry. This type of polish is made up of a polymer, usually nitrocellulose, dissolved in solvent, which is usually ethyl acetate or butyl acetate. In the bottle, the solvent suspends all the components of the polish. Once applied onto the nail, the solvent evaporates, leaving the polymer chains to form a solid film across the surface of the nail. The exposure to air as the polish leaves the bottle will kickstart the evaporation process, but this can also be sped up by your body heat or a fan. On the formula side of things, the ratio of polymer to solvent will also affect the drying time of the polish. Polishes marketed as “fast-dry” will contain a higher amount of solvent. More evaporation means that the liquid in the polish will dissipate faster, leaving the hardened film of colour behind. Other “fast-dry” products can include drops or sprays that also contain solvents or silicones that evaporate instantly, pulling the liquid from the polish along with them. Basically, anything that increases the evaporation rate will cut down the waiting time for your mani-pedi and prevent those pesky smudges.
Gel polish also comes as a liquid formula and is applied layer by layer to the nail. But the key difference is that it needs to be exposed to UV light in order to harden or “dry”. The appeal of gel polish is that it dries faster and lasts longer, when compared to basic polish. Instead of polymers in solution, gel is made up of methacrylate monomers and photoinitiating compounds such as benzoyl peroxide. Ultraviolet light converts the photoinitiator into very reactive species called free radicals that then begin the process of linking the methacrylate monomers into polymers. That polymer is a solid, essentially a thin layer of plexiglass. As this layer forms, it gets into all the little crevices on the surface of the nail and produces a finish that lasts longer than a basic nitrocellulose polish.
Shellac is almost the same as a gel polish, with a slightly different formula that was developed by the company, Creative Nail Design. It combines the UV light system of a gel polish with some of the components of a basic gel polish, and so the chemistry is about the same. That means it still uses the UV light system for the polymers and monomers to fall into place, which explains why my manicure was set using a UV light, instead of a fan.
A nail polish remover is a solvent such as acetone or ethyl acetate in which the polish dissolves. For gel or shellac, a nail technician will start by filing down the surface of the polish, allowing the solvent to penetrate more readily.
The safety of gel and shellac is often scrutinized due to the repeated exposure to UV radiation, a known carcinogen. However, studies have shown that getting this type of manicure every few weeks translates roughly to the same risk as an extra 1.5-3 minutes of sunlight daily every 2 weeks.
The rest of the ingredients include a number of additives that can be found in all these varieties of polishes. Adhesive polymers or plasticizers are added to ensure that this layer sticks onto the nail surface to maintain some flexibility in the polish so that it doesn’t chip easily. Film modifiers can be used to change the finish for a glossy or matte appearance. Arguably the most important part of the polish, the colour, is added through inorganic or organic pigments. Finally, mica or glitter can be added to elevate the polish with a little sparkle. Playing around with the combination of these components can change up the function and finish of your polish — so there’s more chemistry at hand than you might think!
At my convocation ceremony, I thought about all the labs, tutorials, and exams that led up to this moment. And as I started down at my yellow shellac nails, I realized that some of the best chemistry lessons are hidden in our everyday lives.
Cat Wang recently graduated from McGill University with a Bachelor of Science (BSc) degree in the anatomy and cell biology program and is currently deciding on a Master’s program.
