Method of creating and coating a material

A method of creating a material for use as a material to be coated by curtain coating and curtain coating the material comprising the step of:

• forming a freely falling curtain of a composite layer arranged to impinge against a continuously moving receiving surface of said material;
• creating a surface texture of said material such that h(λ)≦Rz, h(λ) being the height of the composite layer as a distance λ from the point of impingement, in which λ is the average periodicity of the surface texture and Rz (DIN4768) being the roughness of the material;
• and the material is coated with a freely falling curtain formed of a composite layer of one or more coating compositions that impinges at a point of impingement against a continuously moving receiving surface of said material having a roughness Rz (DIN4768) as stated above in which the coating composition forming the layer adjacent to said receiving surface has a viscosity, η, measured at a shear rate of 10,000 s−1 such that when combined with said roughness Rz, said curtain gives a value of a specifying parameter φ0 that is greater than 1, where said specifying parameter φ0 is defined by φ 0 = 1818 ⁢ ⁢ σ 1 / 3 ⁢ R z ⁢ { 1 0.0002 ⁢ η ⁢ ⁢ U ⁢ ⁢ cos ⁢ ⁢ θ ⁡ ( 1 + Ω ⁢ ρ ⁢ ⁢ Q 20 ⁢ ⁢ η ) } ;
• in which
• σ is the surface tension (Nm−1) of the layer adjacent to said receiving surface;
• η is the viscosity (Pas) measured at a shear rate of 10000 s−1 of the layer adjacent to said receiving surface;
• θ is the angle formed between said curtain and a normal to said receiving surface at the point of impingement;
• ρ is the average density (Kg/m3) of said one or more coating compositions;
• Q is the total volumetric flow rate per unit width (m2/s) of said curtain;
• and
• Ω is a Lorentzian factor which reduces the influence of momentum when flow rate is high or viscosity is low, Ω being defined by Ω = 25 25 + ( ρ ⁢ ⁢ Q η - 8 ) 2 .