Abstract: A container cover provides a removable cover for placement on the surface of the liquid contents of a container, thereby sealing the liquid contents from the air-filled void of the container. The device includes a disc portion of a size and shape to adequately cover the liquid surface, a handle portion enabling manual grasping of the device for insertion and removal, and a reservoir member, preferably integral with the handle portion, which is saturated with an appropriate thinning agent. This reservoir member is exposed to the lower surface of the disc via perforations, so that it can replenish the volatile components otherwise lost by the liquid contents over time, thereby offsetting the effects of evaporation and oxidation.