Nail polish is made up of four basic ingredients: film forming agents, resins and plasticizers, solvents, and coloring agents. The combination of these ingredients differs, depending on the nail polish brand.
The main ingredient in all nail polish is nitrocellulose. This chemical is used to create a film and bond together all other ingredients used in the nail polish, and it is the most important ingredient in creating a good nail polish. The correct mixture is needed to create a hard film on the top of the nail polish coat that hardens at the right speed to allow all other ingredients underneath time to dry. This chemical is highly combustible and is also used to make dynamite; a subdued version of the chemical is used in nail polish.
The resins and plasticizers give the nail polish flexibility and resistance against soap and water. No set mixture of resins and plasticizers is used universally in nail polish. Each brand creates its own mixture of chemicals according to its independent research.
The next ingredient is coloring pigment that is held together by a solvent that must evaporate as soon as the nail polish is applied. In older versions of nail polish, a coloring dye was used, but modern day nail polish is made with pigments instead.