- Nitrocellulose is key in creating a good nail polish. A hard film must form on the surface of the nail, but it can’t form so quickly that it disables the material underneath it from drying. By itself, however, nitrocellulose is brittle and sticks to nails poorly, so other ingredients are needed to achieve a good coating. Nitrocellulose comes in different viscosities that can match the viscosity wanted in the final product.
Source: health.howstuffworks.com/skin-care/nail-care/tips/nail-polish1.htm