In addition to the many substrates, or paper that is available for the printing of security labels, there is also another layer of security that can be applied: the use of security inks. Indeed, today’s technology has seen the development and successful use of many ink types.
This type of ink offers some sort of visible change when it’s been tampered with. In this case, ‘tampering’ refers to the application of some sort of solvent to the ink in an attempt to remove information printed in the document. Solvent sensitive ink will change colour once a solvent has been applied to it. Some of the documents on which solvent sensitive ink is used include cheques and watermarks.
This type of ink works in much the same way as its solvent sensitive counterpart, causing some sort of visible evidence of tampering once something has been applied to it. In the case of fugitive ink, any water or other liquid that is added to this ink will cause it to smudge the area or pattern it’s been applied to. Even wetting the finger with saliva and running it across fugitive ink can be enough to cause it to smudge.
Also known as OVI, optically variable ink works much in the same way as a holographic image does, changing colour depending on the viewing angle. The most common colour shifts for OVI are red which changes to purple, and brown that changes to green. The secret is in its content of millions of metal flakes. This kind of ink requires printing in a heavyweight. Typically, OVI is used over small areas such as on currency or on a passport, as this ink is quite costly.
Thermochromic ink is temperature-sensitive, which makes it an ideal solution for a wide variety of applications. Thermochromic ink disappears at a certain temperature and reappears when its original temperature has been restored. This ink type is available in 15°C, 31°C and 45°C. This is so that the ink can retain its security in more than one temperature. For example, a 15°C level ink stored in 31°C temperatures would disappear.
This type of ink is also available in a ‘permanent change’ variety. When it reaches its colour-changing temperature, it doesn’t revert to its original colour.
This ink type will only reveal itself to have been tampered with when UV light is applied. It will also glow in the absence of light when it has been tampered with. This type of ink offers a second layer of protection. For example, secondary fluorescing ink may appear as neon green under UV light, but then show bright red if it’s been tampered with.
The authenticity of a product can be verified using biometric ink. This ink type contains DNA tagging agents that can be read by a machine that determines its authenticity. They can also be tested for authenticity by applying a reading solvent. Biometric ink can contain a wide range of varying properties, which only increases the security of the items the ink is used on.
Like its optically variable counterpart, magnetic ink contains small flakes, but of the magnetic variety. Magnetic ink is primarily used for the purposes of numbering and sterilisation. The flakes are read by a machine to determine their number. The MICR numbering on a cheque is commonly printed with magnetic ink, and contains various information including cheque and account number and the bank’s sort code.
These inks can be found in and on many of the goods we use. They can also be chosen when you need to ensure that your products are authentic and/or safe for consumers to use.