Monochrome device fluorescent pantograph

A method comprising:

• forming an original document using a first print medium comprising:
• in a first region of the first print medium, printing a first monochrome pattern with a single colorant, the printed first region including first shapes which are devoid of the colorant, and
• in a second region of the first print medium, printing a second monochrome pattern with the colorant, the printed second region including second shapes which are devoid of the colorant, the second shapes having a smaller size and a higher frequency than the first shapes, one of the first and second regions encoding information;
• the first and second patterns and a fluorescence of the first print medium being selected such that:
• the first and second regions of the original document are indistinguishable to the naked eye, under both normal and ultraviolet illumination;
• and
• in a copy formed by scanning the original document and printing the scanned document on a second print medium with a plurality of colorants, the first and second regions of the copy are indistinguishable to the naked eye, under normal illumination, but are distinguishable to the naked eye, under the ultraviolet illumination, to reveal the encoded information.