Hockey ice in an artificial ice arena is made of numerous thin layers of ice all meshed together and typically kept under an inch thick in total. The characteristic white colouring is a paint added to one of the bottom most layers which aids in the reflection of light and subsequently heat which increases efficiency of both the arena lighting system and the refrigeration plant responsible for keeping the ice frozen. Resurfacing equipment, most commonly referred to universally as "Zambonis" shave a very thin (less than 1/16th of an inch) layer off as they pass, adding a new layer of water to be frozen behind them, typically at temperatures around the 100 degree ferenheit mark as to bond to - and strengthen - the layers below. An average "flood", as this process is called, takes several minutes and dumps 120 - 160 imperial gallons of water onto the ice surface, depending on how aggressively the machine operator is cutting and how deep the grooves are from the skaters using the facility.