Butter Keeper Crock, ceremic stoneware with blue trim. 3 1/2" wide, 3" deep. The butter crock is a two-piece contraption that keeps butter fresh on the counter for up to 30 days. The butter goes in the “bell,” which you place in the water-filled crock. This device keeps butter smooth and spreadable for whenever you need it. Change water every 3 days. The idea of keeping butter in a crock container that is shaped like a bell dates back to the 16th century.