A cosmetic product includes a) a cosmetic preparation including, in relation to the total weight of the preparation, a1) 60 to 94 wt % polar solvent； a2) 0.1 to 20 wt % oxidant； and b) a device for flash-evaporating the cosmetic preparation a). A method for changing the color of keratinous fibers incorporates such a product. Particularly, the cosmetic preparation a) is used as a process material in a flash evaporation device.
