Usually, it takes about three to four hours for the water to freeze in a freezer as ice is made in a standard ice tray — those plastic models with space for a dozen tapered cubes. Water freezes when it reaches 32 degrees Fahrenheit (0 degree Celsius), but the time it takes to do so depends on several factors that may be different in your freezer than in your neighbour’s. The size of the ice cubes matters. If you have an unusual ice tray designed to make very small ice cubes, these will freeze faster than large blocks of ice. In fact, the surface area of the ice will also affect freezing time since ice begins to freeze from the outside to the inside. This means that an ice tray that has air space between each cube will freeze faster than one that merely has dividers. The air temperature of your freezer matters. Generally, most home freezers are set at 0 degrees Fahrenheit, which is optimal. However, if you leave your freezer open or fill it with room-temperature food at the same time you make your ice, you’ll unwittingly raise the air temperature in the freezer, which will slow down your ice-making process.