Abstract: A device for sealing the surface of a liquid in a cylindrical can having an annular lid retaining rim at its upper end defining an opening in the can. The device comprises a rigid circular disk of light weight material sized to pass freely through the opening in the can defined by the rim and float upon the surface of the liquid until a skin forms upon the surface of the liquid between the peripheral edge of the disk and the associated sidewall of the can. A radially disposed cutter is secured at its inner end to its central portion of the disk adjacent the upper surface of the disk. The cutter extends radially outwardly from the center of the disk and has a cutting blade at its outer end located in close proximity to the circular peripheral edge of the disk. A handle on the cutting element intermediate its ends facilitates rotation of the cutting element relative to the disk to move the cutting edge of the blade in cutting engagement with the skin formed on the surface of the liquid.