DE2602812

Surface melting of solid materials or objects, esp. building elements, using an arc as a source of heat, the novelty being that a gas is fed through the arc so that the resulting directed plasma ensures the prodn. of the required heat. The arc is pref. generated using a low voltage direct current, the plasma source being located 2-80 mm from the surface being fused and the axis of the plasma jet is pref. at an angle of 10-90 degrees to the surface. The gas employed is pref. Ar, N2, air, a hydrocarbon, H2 or a mixt. thereof, and the surface may contain an inorganic pigment, esp. metal oxide. Several burners may be used in an automatic program, and a pref. burner design is claimed. Used e.g. for producing a glazed but porous surface on panels 12 m2 in 15 mins., the panels being used as facades in domestic or large industrial buildings using mass prodn. and pre-fabricated building elements. Using a value of 1 for the cost of facades produced by the invention, the use of coloured grey cement with limestone chips is 2.5. times more expensive, and the use of coloured plastics 4-6 times more expensive.