NOVELTY - Coating (A) comprises at least one layer disposed over a substrate (10), where the layer comprises a thickness defined by a first surface and a second surface, the first surface of the layer is closer to a surface of the substrate than is the second surface, and the layer is porosity graded such that pores which are larger in size are located closer to the first surface of the layer and the size of pores in the layer becomes smaller throughout the thickness of the layer away from the substrate and toward the second surface.    USE - The coating is useful as anti-reflective coatings on glass substrates used in photovoltaic devices.    ADVANTAGE - The coating: increases the transmission of light through a substrate; achieves anti-reflective properties with greater consistency; and is produced at fast and consistent rates.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a coating (B) comprising: a first layer disposed over a substrate; and a second layer disposed over the first layer, where the second layer comprises a thickness defined by a first surface and a second surface, the first surface of the second layer is closer to a surface of the substrate than is the second surface, and the second layer is porosity graded such that pores which are larger in size are located closer to the first surface of the second layer and the size of pores in the second layer becomes smaller throughout the thickness of the second layer away from the substrate and toward the second surface;    (2) a method (C) of preparing the coating, comprising: preparing a composition (I) comprising a compound comprising silicon and oxygen, a polymeric glycol, a strong acid, at least two alcohols, a balance of water and, optionally, a compound comprising a metal including aluminum, zinc, tin, titanium and/or zirconium and oxygen; applying the composition onto a surface of a substrate that is slightly heated to a first temperature to form a coating; and heating the coating to a temperature above the first temperature, where one alcohol has a higher boiling point than the other alcohol; and    (3) a method (D) of increasing the transmission of light through a substrate, comprising: preparing the composition (I); applying the composition onto a surface of a substrate that is slightly heated to a first temperature to form the coating; and heating the composition disposed on the substrate to a temperature above the first temperature, where one alcohol has a higher boiling point than the other, and after heating, the transmission of light through the substrate with the coating is increased by at least 1% when compared to the transmission of light through a substrate without the coating.    DESCRIPTION OF DRAWING(S) - The figure shows a single layer anti-reflection coating system.    Substrate (10)    Anti-reflective layer (20)