Security paper and methods for production thereof

A method of manufacturing security paper, the method including:

• (a) forming a light-colored base paper having a non-protection area of a first thickness, and a protection area of a second thickness on at least one major surface of said base paper wherein said first thickness is greater than said second thickness;
• and
• (b) treating a major surface of said base paper with colorant such that the effective quantities and opacities of colorant at the respective protection area and the non-protection area result in transmission of light through the combination of fibers and colorant at the protection area and the non-protection area so as to produce a visually lighter color at the protection area than at the non-protection area;
• and such that the same quantity and opacity of colorant at the respective protection area and non-protection area is sufficiently intense that reflected light attenuation at the protection area is greater than reflected light attenuation at the non-protection area, so as to produce a visually darker color at the protection area than at the non-protection area, when viewed using reflected light.