Methods, compositions, and devices for customizing a cosmetic mask for application to an individual are described herein, and such cosmetic masks include gel-like formulations that, upon heating, can be tailored for specific applications to the individual. The present invention further provides a semi-solid starting formulation comprising a solvent, a wetting agent, a thickener, an acid, water and an effective amount of agar, wherein the semi-solid starting formulation forms a hydrogel upon heating. In particular, the semi-solid starting formulation, when heated, is applied to the skin of an individual while maintaining warmth, and then forms a gel-like material when the formulation cools sufficiently on the skin.