A manicure is subject to a lot of abuse as the wearer goes about their daily life (opening jars, cooking, typing on a keyboard).
repeat purchase of a nail polish, it must be able to stand up to this
type of use. As well as the adhesion properties mentioned above, the
stiffness and toughness of a polish are all extremely important.
overly stiff, brittle polish would be undesirable as it would break
when a nail is bent when opening a soda can, for example. The low
stiffness is important for the polish to follow the nail as it bends. A
high strain to failure is also crucial, or the polish film would break
under the slightest deformation.