An overnight mask is not applied to be washed off before bed. It goes on as the last step of the evening routine, over everything already applied, and stays there until morning, when the face is simply rinsed. Hence the wording in the directions — "last step": the layer belongs above the others, not beneath them.
With some, the mask takes the place of a night cream and is spread in a thin, even layer over the whole face. With others, it goes on top of the cream. Which of the two it is appears on the packaging, so the directions are worth a look before the first use.
Overnight care also comes in a firmer form: a gel mask that is worn rather than spread. It follows the contours of the face and stays put while you sleep; the directions call for at least two to three hours of wear, or a full night — safety beyond eight hours has been confirmed in clinical testing. Some masks even signal when they are done: as the active ingredients pass into the skin, the layer turns from opaque to clear, so in the morning you can see the mask has finished its work and simply lift it off.
A sleeping mask earns its place when skin needs more time than an evening allows. Instead of fifteen minutes at the mirror, the product works for as long as sleep lasts.
