Bubbles may be the result of excessive shaking of the bottle before painting. Before applying the nail polish, it is advisable to mix the contents of the bottle, especially if you reach for a given shade after a longer period of time. However, excessive shaking will cause air to get incorporated in the liquid nail polish in the form of small bubbles and you will then unknowingly apply them during painting. Instead of shaking the bottle up and down, gently roll it in both hands to mix the contents without creating air bubbles.