Steel milk cans were commonly used by farmers into the mid-1900s to transport their milk. The milk cans usually had the name of the dairy farm or a number to make sure it was returned to the farmer. In the early 1960s many farmers started to use bulk tanks, as these tanks could hold much more milk at one time. Tank manufacturers experimented with glass, nickel, aluminum, and steel. However, they found that stainless steel was the best material to use because it was easier to sanitize, or clean, and kept the milk cold. By the 1980s, almost all dairy farmers used bulk tanks to store their milk.