Security Ink Types

When considering the printing of security labels, you should know that there are several different types to choose from. To be exact, there are eight types of ink that are used for security purposes. The most common applications for the use of security ink include cheques, passports and security documents.


This ink type is also known as solvent sensitive. Reactive ink will tell a person if any alteration has been attempted. Attempts to remove this type of ink usually occur on items like cheques, where variable printed information exists. Reactive ink is most commonly used in the security of printed watermarks.


Thermochromic ink is temperature-sensitive, appearing or disappearing when exposed to varying temperatures. This type of ink is available in a wide range of sensitivities, but the most common temperatures are 45, 31 and 15 degrees Celsius. When considering this ink, it’s important to determine the conditions that the ink will be exposed to, as ambient temperature can affect visibility.

Optically Variable

This type of ink is also called OVI. Optically variable ink has tiny flakes of metallic film which changes the colour set as the viewing angle is altered. This very expensive option needs to be printed in heavy weight for optimal effectiveness and usually appears on currency, passports and the like. Most commonly, the colour of optically variable ink will change from brown to green and vice versa, or red to purple and vice versa.


In the UK, invisible ink is used for the purposes of document protection as well as cheque printing. Invisible ink’s most common form is the invisible ultraviolet type, which is only visible when the print is placed under a black light source. The only way to make this ink visible under a black or UV light source is to apply it to a UV dull substrate such as paper or card stock.

Water-Based Fugitive

Fugitive ink reveals tampering much in the way that reactive ink does. When an attempt is made to alter some aspect of a document using water or another liquid, fugitive ink will run, effectively smudging any area or printed pattern. Fugitive ink is found on cheques, and all that’s needed to test for this type of ink is to wet your finger with saliva and run it across the cheque’s printed background.


Where security for serial numbers and other numerical sequences is desired, magnetic ink is the typical solution employed. This type of ink contains tiny magnetic flakes which communicate with an electronic reader to verify a document, such as a cheque. Magnetic ink is in use on the MICR numbering portion of cheques manufactured in the UK. The MICR number contains sensitive information including account number, sort code and cheque number.

Secondary Fluorescing

Where fluorescing ink glows or becomes visible under UV light, secondary fluorescing ink does not do so unless some sort of alteration attempt has been made. This ink is used to protect against alteration and tampering. Usually, secondary fluorescing ink will appear green when exposed to UV light, but will include a red secondary shade which will show if any tampering has been attempted.


As its name suggests, biometric ink contains DNA tags. A machine can read these tags, or they can be manufactured to react when they come into contact with a particular solvent. Biometric ink works best in situations where verification of a genuine product is needed. Biometric ink can also contain a different set of biometric properties for each batch of documents that is printed. Validating the authenticity of a product marked with biometric ink requires specialist methods to be used.

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