to pick up excess water. This water is then filtered through a screen and recirculated. Finally, a layer of water is laid down to fill in the remaining grooves in the ice. The ice-making water is released through a sprinkler pipe at the rear of the conditioner, which wets the cloth towel that is dragged behind the resurfacer. The towel ensures a smooth, controlled deposition of water. Traditionally, hot water has been used because it slightly melts the layer of ice below it, leading some operators to believe it forms a stronger bond during the freezing process because heating the water releases dissolved gases thus allowing the ice to freeze in a clearer state. It is also sometimes believed that warm water reduces the freezing time of the water due to the unproven Mpemba effect. The water used in some rinks is also filtered and treated before being used in the ice resurfacer to remove any minerals or chemicals in the water. These impurities can otherwise make the ice brittle, soft, give it undesirable odors, or change the color and clarity. Many ice resurfacers are fitted with a "board brush", a rotary brush powered by a hydraulic motor. The board brush is extended and retracted on the left side of the machine by a hydraulic arm. This allows the operator to collect ice shavings and debris that accumulate along the edge of the rink (along the kick plates below the dasher boards of the rink) where the conditioner cannot easily reach. The brush sweeps the accumulations into the path of the conditioner, which removes them from the ice. The use of a board brush can dramatically reduce the need for edging of the rink. After resurfacing the entire sheet, also known as an "ice cut" or "flood", the snow container must be emptied. Hydraulics raise one end of the container, causing the snow to spill out. Smaller, cheaper machines have also been designed to provide a smooth ice surface in a manner similar to a traditional resurfacer. These can be either self-propelled or pushed/pulled by the operator. Self-propelled vehicles typically incorporate the main components of full-size ice resurfacer, including a blade and water tank, but on a smaller scale. These are usually mounted to an ATV or golf cart-like vehicle. Ice edgers The ice around the edges of a rink has a tendency to build up because the conditioner blade