Abstract: Liquid-impermeable sheets, suitably composed of aluminum foil, are provided with a coating of pressure-sensitive adhesive, preferably adjacent one edge of the sheet, and optionally, a strippable cover to protect the adhesive prior to use. The process comprises separating a portion of hair to be treated from the remaining hair on the head, adhering one of the liquid-impermeable sheets to the scalp and hair of the head immediately adjacent and below the roots of the portion of hair to be treated, and treating the selected portion of hair with any desired liquid-treating agent such as a bleach or dye and permitting the treated hair to overlie the central portion of the liquid-impermeable sheet while the treating agent takes effect and, optionally, folding or rolling the sheet toward the head and then folding the edges inwardly to form an envelope, thus isolating the treating agent from the remainder of the head of hair and treating only the selected portion of hair.