A face mask is not one product but several formats, and what separates them is what happens after you put it on. One is peeled off, another is rinsed away, a third stays on the skin until morning. Once that distinction is clear, choosing gets much easier.
A sheet mask is a cloth soaked in essence: it sits on the face for ten to fifteen minutes, comes off, and the essence left behind is patted in rather than rinsed. A hydrogel mask has no cloth at all — the gel itself is the essence in solid form and hugs the contours of the face; how long it stays there depends on the specific mask: some come off after fifteen to twenty minutes, others are made to be worn for hours. Clay and cream wash-off masks usually take ten to fifteen minutes and are removed with lukewarm water.
An overnight mask follows a different order. It goes on in the evening as the final step, a thin layer over your moisturizer or in place of it, and stays there until morning, when the face is simply washed with lukewarm water. The line between that and a hydrogel is not sharp: some hydrogel masks are designed to be worn for several hours, or even overnight.
The difference between these formats is not that one is stronger. It is how long the product stays on the skin and whether it is rinsed afterwards — and that decides when it fits into your day: fifteen minutes in front of the mirror, or a layer that works while you sleep.
