copying). Thermochromatic ink that fades when rubbed. Microprinting Phosphorescent fibres in the paper that can only be seen in UV-light, or fibres visible in daylight. Metallised threads. Usage of a pattern in the paper which only appears upon prolonged exposure to UV-light or oxygen (e.g. to indicate expiry). Holographic images Scratchable surface, e.g. on lottery scratchcards, gift cards, or phone cards; to indicate when information has been revealed. Chemical sensitisation of the paper, e.g. ink erasers or sensitivity to acids/alkalines. Taggants added in the coating or in the base paper; chemical "DNA" that can only be decoded by special means and acts as a unique identifier. A note on the paper describing the security measures, so they can be checked. The most sophisticated techniques are used with paper money – see Counterfeit money: Anti-counterfeiting measures for discussion. See also Holography Metallizing Phosphorescent Banknote processing References External links Security Paper at International Paper Knowledge Centre Paper products