NAILPOLISH
Nail polish can be historically traced back approximately 5,000 years, to at least 3000 BC, when it originated in China. During the Ming Dynasty, Chinese nail varnishes and lacquers were synthesized from a combination of beeswax, egg whites, gelatin, vegetable dyes, and gum arabic. The Egyptians were known to use orange henna to stain their fingernails. In China as well as in Egypt, color symbolized particular social classes. During the Chou Dynasty (600 BC), gold and silver were the royal color choices, and later, royalty preferred black and red and thus applied these colors to their nails to indicate their status.
Modern nail polish is actually a refined version and variation of auto- mobile paint. The polish, designed to protect and beautify nails, is a highly specialized and flexible lacquer that does not easily crack and flake with natural nail movement. The formulation goal of most manufactur- ers is to provide as much film as possible in a single application coat while retaining application ease, quick drying time, maximum hardening, chip resistance, and a natural pearl essence. Usually, the application of two coats is necessary to obtain adequate film thickness and sufficient opacity. The three major ingredients in most nail polish brands are organic sol- vents, resins (thickeners or hardening agents), and color pigments. The most common organic solvents are ethyl acetate and butyl acetate (both also used as solvents in nail polish removers). As volatile solvents, these esters (synthesized by reacting a carboxylic acid with an alcohol; the gen- eral formula is R-COO-R′) evaporate quickly, leaving the resin/pigment mixture attached to the nail surface as a thin coating. Other commonly used solvents include acetone, toluene, methyl chloroform, dipropylene, ethyl alcohol, and isopropyl alcohol. Solvents are responsible for the strong odor of nail polishes.
Resins, types of polymers, are the thickening and hardening agents that, without pigments, serve as colorless nail protectors resembling clear furniture lacquer. These agents include nitrocellulose (collodion) and dif- ferent acrylate and polyester/polyurethane copolymers. Copolymers include chemicals such as methacrylic acid, isobutyl methacrylate, toluenesulfona- mide formaldehyde resin, phthallic anhydride/trimellitic anhydride/glycol copolymer, tosylamide/formaldehyde resin, and dimethicone copolyol.
Nail polish pigmentation (coloring) tends to be the essence of the pol- ish and of paramount importance to the consumer. A variety of D&C laked dyes (drug and cosmetic dyes approved by the FDA) are used in combination to achieve the desired color. Coloring may also be attribut- able to the presence of chemicals such as chromium oxide greens, chro- mium hydroxide green, ferric ferrocyanide, ferric ammonium ferrocyanide, stannic oxide, titanium dioxide, iron oxide, carmine, ultramarines, and manganese violet. Sparkling and reflective particles such as mica, bismuth oxychloride, natural pearls (guanine), and aluminum powder are used to make “frost” and “shimmer” polishes appear glittery or pearl-like.
Other ingredients in nail polish include plasticizers (e.g., dibutyl phtha- late, camphor, citrates, adipates, glycol dibenzoate) that serve as molecu- lar lubricants, allowing the resin to remain flexible after drying, and increase resin resistance to oil and water. Dispersants (e.g., organically modified clays such as stearalkonium bentonite and stearalkonium hec- torite) are additives that control flow by helping the pigments mix with the resin and solvent, thereby preventing sinking of the color particles. Ultraviolet stabilizers (e.g., benzophenone-1) may be added to prevent the polish from changing color after excessive UV sunlight exposure. In addition, chemicals such as colorant consistency regulators (e.g., palmitic acid) and antioxidant preservatives (e.g., citric acid) may be added.
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