Security Printing Inks

from Warner, Richard D. and Richard M. Adams II, Introduction to Security Printing. (Pittsburge: PIA/GATF Press, 2005).

There are two types of security printing inks. Anti-duplication inks are meant to prevent, you guessed it, unauthorized copying. They are usually a covert security feature. Anti-alteration inks are an overt feature, and they are used to indicate when there has been tampering with water or chemicals. Manufacturers of security inks will only sell to authorized customers.

Anti-duplication inks:

  • Trademark colors, metallic inks, and conventional fluorescent inks are all extremely difficult to replicate with commercial equipment like scanners and copy machines.
  • Iridescent inks “contain metallic particles and exhibit a change of color and surface texture when viewed at different angles.”
  • Color-shifting inks are “used on US currency for denominations of $5 and higher. The ink changes color from black to green, or in the newest banknotes from green to copper, as the bill is tilted back and forth in front of the observer.”
  • Up-converters/down-converters (seems like a great little moment of jargon)
    • Up-converters/down-converters refer to inks that are usually invisible to the human eye under normal lighting conditions, but are visually detectable with either UV or IR radiation.
    • Down-converters absorb UV radiation and re-radiate at lower energy levels (longer wavelengths) toward the red end of the visible spectrum.
    • Up-converters absorb infrared radiation and re-radiate higher energy (shorter wavelengths) of light in the blue end of the visible spectrum.
  • UV inks:
    • UV-visible/daylight-invisible inks can be seen only when illuminated by UV radiation.
    • Visible fluorescent inks are daylight visible, and may also “show up as an unwanted image during attempts to scan or photograph it for unauthorized reproduction.”
    • Invisible UV-fluorescent inks are a covert security feature == they’re transparent or colorless in normal light but glow different colors under UV light.
  • Metameric pairs are “inks that appear similarly in color under one set of lighting conditions but have noticeably different optical properties under another set of lighting conditions.”

Anti-alteration inks:

  • Erasable inks are “used to discourage the alteration of documents by mechanical efforts, such as scraping the ink images with a razor blade to remove them. The ink is easily removed but leaves visual evidence of tampering after removal or alteration.”
  • Fugitive inks “are reactive to either water or solvents and usually leave an unwanted stain on the document if alteration has been attempted.”

 

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