Security fiber paper is made by addingcolored (red, blue, etc.) fiber or colorless fluorescence fiber into the paperpulp and can be divided into colorful fibers and colorless fluorescence fiber.The former type is visible with naked eyes on the surface of the paper, and thelatter one is only visible under the ultraviolet rays with the colors of red,blue or orange, etc. They can be thick or thin, short or long. Fiber usuallydistributes in a random way, therefore the density is different in differentplaces.