Nail polish thinner is a chemical solution that restores thickened nail enamel to its original consistency and helps prolong the life of the nail polish. Nail polish that is too thick may result in enamel that is difficult to apply and/or does not last as long on the nail as nail polish that is the correct consistency.

The correct consistency of nail polish should allow one to apply at least two coats of enamel before needing to redip the brush.