Ice cream–making equipment had improved over the years, and quantity production was possible by the early part of the twentieth century. By 1910 continuous-process freezers could produce up to 150 gallons of ice cream an hour. During World War I, ice cream making was banned in England. In the United States, sugar was restricted, so ice cream makers began replacing some of it with corn syrup and corn sugar. See corn syrup. Some manufacturers used powdered milk and butter in place of the more expensive fresh cream. When the war ended, some substitutions continued.