Hic Earthenware Cermic Butter bell / crock / keeper The major difference between a butter dish and a butter crock is that a butter crock uses water to seal off the bottom of the butter from the air, keeping it fresh for longer than butter exposed in a butter dish. Load your butter into the big dish inside of the lid and then add water to the main container. The butter is suspended upside down, sealed off by the water. Works best with salted butter.