What is the main component of a nail polish formula?

The primary component of a nail polish formula is nitrocellulose. Nitrocellulose serves as the film-forming agent, providing the necessary properties that allow the polish to adhere well to the nail and to create a smooth, even finish when applied. It also contributes to the overall durability and shine of the polish after it dries.

Acetone, while relevant in the context of nail products, is primarily used as a solvent for removing nail polish rather than as a component in the formulation of the polish itself. Formaldehyde is sometimes found in nail hardeners and other nail products for its strengthening properties but is not a central ingredient in standard nail polish formulas. Ethyl acetate is a solvent used in nail polish, but it does not form the film that is crucial for the performance of the polish. Thus, nitrocellulose is the cornerstone of nail polish formulations, making it the correct choice in this context.