I could never keep my nails painted in Organic Chemistry. Wash bottles full of acetone rested around the lab, and we used them to clean the equipment more often than soap and water. Crusty organic solids on our test tubes and on my fingers were unaffected by traditional cleaning methods, but acetone stripped them away. This occurred because acetone is a powerful solvent, meaning it can quickly dissolve solid chemicals. This convenient chemical reaction made cleaning our test tubes easy and keeping my nails painted a challenge.
Ironically, cosmetic chemists use the same type of chemical reaction to create nail polish. They take a solvent, one that is weaker than acetone, and they dissolve multiple types of chemicals, or solutes. In nail polish, the solutes are responsible for the most recognizable properties: glossiness, color, adhesiveness, and strength.
Arguably the most important and most common solute in nail polish is nitrocellulose. It adheres to the nail and creates a glossy film over the coat of paint. This versatile ingredient is also essential for making dynamite, smokeless gunpowder, movie film, and even ping pong balls. However, the nitrocellulose in dynamite or gunpowder is not the same as nitrocellulose in nail polish; the differences all depend on the nitrogen content.
To make nitrocellulose, a chemist dissolves a common organic fiber called cellulose in nitric acid. Cellulose is found in our clothes and paper, and it originally comes from plants. In their cell walls, cellulose helps them stay firm upright. Nitric acid, in contrast, is toxic, highly corrosive, and can cause severe burns. If a chemist adds more nitric acid to the reaction, they produce nitrocellulose with 12.5% nitrogen, or guncotton. It’s fluffy, white, and very explosive, making a perfect material for dynamite. If the chemist adds less nitric acid, they produce nitrocellulose with only 10.5-12.5% nitrogen. This variant is more stable, less flammable, and it can dissolve in alcohols, making it ideal for nail polish.
With only nitrocellulose and a solvent, a chemist can make a simple, clear lacquer, but the chemistry gets more creative when they add color. It is the most identifiable property of polish, and the most chemically variable. Chemists produce green polish with chromium oxide, red and orange polish with iron oxide, and blue polish with ferric ferrocyanide, and they can add multiple other pigments similar to those in food coloring to create vast lineups of colorful shades. Because many people use nail polish as a unique and impermanent accessory, the chemistry of color constantly evolves with public interest and trends.
However, even vibrant colors are not enough to make the best polish. Many customers, myself included, would say that an ideal nail polish should also last several days in near-perfect condition, should be flexible, and should be pleasant to use, in addition to having a strong color. Attempting to achieve this elusive perfect polish, many brands vary their chemistry.
Chemists can make a nail polish chipping-resistant by adding a bit of tosylamide-formaldehyde resin and plasticizers, like camphor, which add strength and flexibility respectively. They can make the polish easier to apply by adding a thickening agent such as stearalkonium hectorite, which keeps the chemicals from separating in the solvent. They might also want to protect the vibrant colors from fading in the sunlight, so they add ultraviolet filters such as benzophenone-1. The list of additions goes on, to the point that many companies have 20+ different chemicals in their polishes, and they’re rarely the same across brands. Despite this variation, however, there is consistency. All nail polishes depend on solvents.
In retrospect, solvents are the simplest part of nail polish chemistry, and they are essential to every step of the process from manufacturing, to applying, to removing a polish. As chemists create new lacquer, they mix together all of the solutes and dissolve them in a solvent such as alcohol, ethyl acetate, or butyl acetate. The solvent keeps these compounds suspended in liquid, and the resulting solution is poured n into a 0.6 fl oz. glass bottle.
When you purchase a new polish, you pick up where the chemists left off. Before you paint, you shake the bottle, and a tiny metal ball mixes the solution, keeping everything dissolved. This step is essential, otherwise the polish will be difficult to work with while you paint. After you apply the wet polish to your nails, the solvent will evaporate in a few minutes, and leave behind the familiar dry, glossy precipitate of a completed manicure.
After several days, you might grow tired of the color, or the inevitable chipping could become irritating. Once again, a solvent is the key. If you’re ready to remove your nail polish, you can perform the same chemical reaction that frustrated me every week in Organic Chemistry. You’ll apply acetone to your nails, dissolve the polish, and wipe it away with a cotton pad or cloth, leaving your nails clean and ready for the next color.
Commentaires