Abstract: A latent image printing method and apparatus uses a substrate with one main surface having a covering comprising one of a first pair of a color developer and color former dye defining a background color in conjunction with the one main surface, wherein the color developer and the color former dye react when mixed to produce a first spectral response which is visible relative to the background color and a continuous coating over the covering which is non-porous with respect to the other of the pair and solvent-resistant to the other of the pair. The coating above selected portions of the covering corresponding to a desired latent image is removed.

Abstract: A latent image printing method and apparatus uses a substrate with one main surface having a covering comprising one of a first pair of a color developer and color former dye defining a background color in conjunction with the one main surface, wherein the color developer and the color former dye react when mixed to produce a first spectral response which is visible relative to the background color and a continuous coating over the covering which is non-porous with respect to the other of the pair and solvent-resistant to the other of the pair. The coating above selected portions of the covering corresponding to a desired latent image is removed.

Abstract: Paper is provided with resistance to photocopying or transmission by telefacsimile by spatial spectral modulation of the paper reflectance at a specific single or preferably multiple frequencies. Such paper has a colored pattern of at least two colors repeating in at least one dimension of a face of a paper with at least one frequency in the range of from about 0.5 to about 50 times per cm. The colors contrast with black or similar dark color to permit black or similar dark colored information to be visible readable when applied to the colored pattern. The colors also cooperate with such information to provide a document resistant to photocopying and transmission by telefacsimile.