Method and apparatus for treating a surface of granite with a high temperature plasma jet

An apparatus for treating the surface of a body of hard material constituted by natural rock and/or artificial stone-like material, comprising:

• first means for producing a high temperature jet of plasma projected onto said surface;
• second means for producing a high speed jet of cooling fluid projected onto said surface;
• mechanical support means on which said first and second jet producing means are mounted;
• and
• means for moving said support means relative to said surface sufficiently rapidly to enable the high temperature plasma jet, projected onto said surface, to suddenly heat only a thin layer at said surface of said hard material, wherein said jet of cooling fluid follows the jet of plasma on said surface;
• in operation, the high speed jet of cooling fluid suddenly cooling the thin layer at said surface just heated by the plasma jet (a) to cause a thermal shock which bursts particles of said hard material at said surface and (b) to prevent deep penetration of heat in the hard material of said body, and said high speed jet of cooling fluid blowing said particles off said surface.