text: The friction coefficient for ice, without a liquid film on the surface, is measured to be . A comparable friction coefficient is that of rubber or bitumen (roughly 0.8), which would be very difficult to ice skate on. The friction coefficients needs to be around or below 0.005 for ice skating to be possible. The reason ice skating is possible is because there is a thin film of water  present between the blade of the ice skate and the ice. The origin of this water film has been a long-standing debate.
  There are three proposed mechanisms that could account for a film of liquid water on the ice surface:
  * Pressure Melting: James Thomson suggested as early as 1849 that  expansion of water as it freezes implied that ice should melt upon compression. This idea was exploited  by  John Joly   as a mechanism for ice skating, arguing that the pressure on the skates could melt ice and thereby create a lubricating film (1886). 
  * Premelting: Previously, Faraday and Tyndall had argued that the slipperiness of ice was due to the existence of a premelting film on the ice surface, irrespective of pressure. 
  * Friction:  Bowden instead argued that heat generated from the ice skates moving, melts a small amount of ice under the blade.
  While contributions from all three of these factors are usually in effect when ice skating, the scientific community has long debated over which is the dominating mechanism. For several decades it was common to explain the low friction of the skates on ice by pressure melting, but there are several recent arguments that contradict this hypothesis. The strongest argument against pressure melting is that ice skating is still possible below temperatures under -20 °C (253K). At this temperature, a great deal of pressure (>100MPa) is required to induce melting. Just below -23 °C (250K), increasing the pressure can only form a different solid structure of ice (Ice III) since the isotherm no longer passes through the liquid phase on the phase diagram. While impurities in the ice will suppress the melting temperature, many materials scientists agree that pressure melting is not the dominant mechanism.
  The thickness of the water film due to premelting is also limited at low temperatures.  While the water film can reach thicknesses on the order of μm, at temperatures around -10 °C the thickness is on the order of nm.
  Although, De Koning et al. found in their measurements that the adding of impurities to the ice can lower the friction coefficient up to 15%. The friction coefficient increases with skating speed, which could yield different results depending on the skating technique and speeds.
  While the pressure melting hypothesis may have been put to rest, the debate between premelting and friction as the dominant mechanism still rages on.