The majority of security inks work in conjunction with security paper. Chemically reactive inks bleed when solvent falsifying reagents are utilised in attempts to alter information. Visible fluorescent and invisible inks (also chemically reactive) are available which fluoresce when irradiated by ultra violet light. Penetrating inks, mostly used for crossings, make it difficult to mechanically lift off cheque crossings as the ink seeps deep into the paper, giving a light mirror image on the reverse.
Thermocromic ink, which is heat sensitive, disappears when subjected to temperatures in a specific heat range. Infra-red reactive ink which can only be seen by utilising equipment that can detect a long wavelength as the reel end of the visible spectrum are also available.
Security Inks used must be appropriate and effective to the requirements of the document and/or to the areas of the document which may be altered. As no system is infallible, a co-ordinated approach combining a variety of features is the most effective. Security inks form part if this approach by helping us to ensure authenticity of the value document as well as assisting in preventing unauthorised alteration by mechanical or chemical means.
