Consumers like to change the appearance of their nails and the most common way to do this is to use nail polish.
What Nail Polish does
Nail polish is a liquid solution applied to the fingernails or toe nails to change their appearance (usually colored) and to protect from chipping and breaking.
The way nail polish works is that after it is evenly spread on the nails, the solvent evaporates and it creates a protective film that resists removal. A colorant or shine agent is also included to improve the nail look.
How nail polish works
Nail polish contains a variety of ingredients to produce a useful, colorful film. The primary ingredient is a film former such as nitrocellulose. This organic polymer forms a continuous, even coating on the nail. Nitrocellulose is used because it is particularly tough and wear resistant.
Film modifiers are required to improve the adhesion of the nitrocellulose to the nail and to increase the gloss. The most common ingredient for this is toluene sulfonamide/formaldehyde resin (TSFR). Because of sensitization issues, chemists continue to look for alternatives. Plasticizers like dibutyl phthalate and camphor are used to improve the flexibility of the film.
After the film creating and modifying ingredients, color additives are the next most important. These are typically insoluble pigments that won’t stain the nail. Bismuth oxychloride and mica coated with titanium dioxide are frequently used.
Finally, a solvent that can carry the formulation ingredients but will quickly evaporate is needed. Toluene used to be frequently used but regulations now limit its use. Alkyl ester and glycol ethers are now more common solvents.
Below is an example of a typical nail polish formula. (Click to expand)
Read more on nail polish from Chemical and Engineering News.