roller 12 meshes with the bottom roller 14 a substrate b passing through the nip will receive a rippled surface such that when the marred substrate is connected to a lightsource light will emit from the ripples alternatively only one roller may be serrated as with the previous embodiments the pressure in the nip may be adjusted during marring and or the gap between the rollers may be greater at one end of the roller than the other referring to fig9 a second alternative embodiment of the marring apparatus is shown in schematic form wherein the top roller 12 is horizontal and the bottom roller 14 is pivotable vertically about one end pressure in the nip will increase or decrease from one end of the rollers to the other depending upon the angle between the rollers alternatively the top roller 12 or both rollers may be pivotable at one or both ends the top roller 12 may be rotatably supported from above by supports 96 98 e g by a structural frame or cantilevered beam not shown the bottom roller 14 is supported at one end through a flex joint 97 that permits rotation the other end of the bottom roller 12 is supported by a hydraulic pneumatic or other lift device 99 that can raise or lower the bottom roller thus adjusting the angle between the rollers alternatively the bottom roller 14.