What types of security inks are there?

Security inks are available to protect printed materials in different guises.

Invisible Ink

One of the most widely used inks is invisible ultra violet and will be revealed when the print is placed under a black lamp (or UV light source). The ink is invisible to the eye (covert) under normal lighting conditions. When passed under a uv lamp the ink glows and is used predominantly for cheque printing and document protection in the UK. It is relatively cheap and is available in many colours. The ink must be applied to a UV dull substrate otherwise it will not be visible.

Thermochromic Ink

Thermochromic inks are sensitive to temperature changes and will appear or disappear at different temperature ranges. If you were to apply a finger and thumb to a 15 °C dark blue printed thermo spot the ink would disappear to nothing and as soon as you removed the heat source the ink would re-appear again. Inks come in various temperature sensitivities and common temperatures available are 15°C, 31°C and 45°C. An important consideration would be where the ink is to be located. In hotter climates you may well have to go for a higher temperature as the ink could be invisible from the ambient temperature itself. Some are available as a permanent change. e.g. when it has reached a temperature the ink colour does not reverse – this may be used on labelling for food product packaging where you could see if an item has thawed out and would be dangerous to re-freeze again.

Solvent Sensitive Ink (reactive)

As the name states, would present a visible indicator that the ink has been attacked by a solvent (usually attempt to remove variably printed information such as a cheque). You will mainly find this being used on a printed watermark or fine guilloche artwork design. Once a solvent has been applied the ink will change colour to show that alteration has been attempted.

Optically variable ink

OVI’s contain minute flakes of metallic film. As the viewing angle is altered the colour morphs from one to another. This needs to be printed with a fairly heavy weight to get the best results. The inks are very expensive and are usually printed in small areas. Such examples would be in currency printing and visa’s. The most common colour changes are brown to green (and vice versa) as well as red to purple. You will also notice that the ink feels almost embossed on the substrate which is due to the amount of ink required to get the required effect.

Magnetic Ink

Magnetic inks are mainly used for serialisation and numbering purposes. The ink contains small magnetic flakes and allows a number to be machine read. The most common application is is cheque printing and you will find it on the MICR numbering portion of the bottom of a cheque. This will usually contain the cheque number, account number and sort code of the bank.

Biometric Ink

Biometric inks contain DNA taggants that can be machine read or react to a reading solvent. This allows for verification of a genuine product and each batch of printed documents can contain different biometric properties. These are completely covert but require specialist methods to validate the authenticity.

Fugitive Ink (water based)

Fugitive ink works similarly to solvent sensitive ink in the fact that any form of alteration (with water or an aqueous solution) will make the ink run so that the printed pattern or area becomes smudged, therefore indicating that a forgery or alteration has taken place. These, again, will be found on cheques and if you are to wet your finger with saliva and wipe across the background, you would see the ink smudge.

Secondary Fluorescing Ink

This ink works in the same way as fluorescing ink however it will not glow or show under a UV lamp UNLESS alteration has occurred. This is a secondary measure to protect against tampering and alteration. Quite often you will have an invisible ink that fluoresces green under a UV lamp and a secondary ink that will fluoresce red so that tampering or alteration is obvious.

Bleeding Ink

Bleeding ink prints in black but when exposed to any aqueous solution it will produce a red stain. Authenticity of a document can easily be tested without the use of any special agents. User can just wet a finger and run it across the ink to instantly see the affect of the bleeding ink. This ink is only available for use on dry offset printing.

Coin Reactive InksThe image printed from this ink is white or transparent. The image is revealed when the edge of a coin is rubbed over the ink. This provides for immediate verification of document authenticity without the use of any special devices. Coin reactive ink cannot be scanned or copied. This ink is available for use with wet or dry offset and flexographic printing.

Erasable Ink

Erasable ink is used on the background of a document so that when an attempt is made to erase information, the ink rubs off in that area. The ink will also react in the same manner as solvent/chemical reactive inks do, giving you two security features in one. Erasable inks are used on scenic or pantograph backgrounds on checks and certificates. This ink is not recommended when imprinting a document through a laser printer. The high temperatures associated with laser printers will cause problems within the printer when erasable ink is used. Erasable ink is available for wet or dry offset printing.

Pen Reactive Ink

A transparent ink that  becomes visible with the use of a special felt tip pen. The use of the pen is necessary to verify authenticity but can also be used to void a document that is no longer in use. Pen reactive ink is available for dry offset printing.

Heat Reactive – Irreversible

Heat reactive-irreversible ink is colorless when printed. When it is exposed to heat between 185°F (85°C) and 212°F (100°C), sharp color appears and does not disappear once the temperature is lowered. This feature helps protect documents or sealed envelopes from being tampered with by the use of steam or heat. Heat reactive-irreversible ink is only available for use on dry offset presses.

Visible Infrared Inks

Infrared visible inks are available in readable and disappearing ink. When printed they can look the same but when viewed under infrared light, one will be readable and one will disappear. One example of using these two inks as a security feature would be to print a bar code using both inks. Print the actual readable area of the bar code with the infrared readable ink and other areas of the bar code with the infrared disappearing ink but making it look like a regular bar code. When read by a bar code scanner, only the infrared readable is read by the scanner. If a forger tries to duplicate the bar code as it looks on the printed document, using regular inks, the bar code would be rejected when read by the scanner because the scanner would read the entire bar code. Visible infrared ink is available for wet or dry offset printing.

Optically Variable Inks

The color of optically variable ink changes when viewed from different angles. The special effect from this type of ink cannot be duplicated by a scanner or copier. A small area of a document could be printed in this ink to verify authenticity.

Penetrating Ink 

Penetrating inks contain a penetrating red dye that goes into the fibers of the paper and will show through to the back of the document. Penetrating inks are commonly used on the arabic and MICR numbering of negotiable documents to deter forgers from trying to scrape the number off from the document. If the number is scraped off the red stain remains on the document. Also, if these documents are duplicated, the reproduction could be easily spotted by checking for the appearance of the red stain on the back of the document. Penetrating inks are available for letter press or wet offset printing.

Photochromic Ink

Photochromic ink can be colored or colorless. When it is exposed to UV light it instantly changes colors. Once the source of UV light is removed it will change back to its original color. The unique properties of photochromic ink cannot be reproduced by a scanner or copier. The authenticity of a document with photochromic ink on it can easily be checked by exposure to sunlight, UV lights or other strong artificial lights. This ink is available in wet or dry offset and flexographic printing.

Solvent/Chemical Reactive Inks

This type ink reacts to solvents or chemicals, such as bleach, alcohol or acetone. The solvents or chemicals are used by a forger to wash away or alter information on a document. When exposed to the solvents or chemicals, these inks will run, change color, or cause a stain to develop. Tampering is easily detected when chemicals or solvents are used on these inks. Solvent/chemical reactive inks are available for wet or dry offset printing.

Thermochromic Ink

Thermochromic ink changes color when exposed to heat and then changes back to its original color when cooled. When an area of a document is printed with thermochromic ink, it can easily be tested for authenticity by holding or rubbing the area between fingers to activate the color change. This property cannot be reproduced by a copier. Thermochromic ink is available for wet or dry offset printing and flexographic printing.

Water Fugitive Ink

When water fugitive ink comes in contact with water or any aqueous type of solution, it will run and stain the document. If a forger tries to wash away an image it would be very obvious. Water fugitive ink is available for dry offset printing.
UV Invisible Fluorescent Inks

UV invisible fluorescent ink is transparent white or colorless and can only be detected under ultraviolet light. If a portion of a secure document is printed with this ink, it can be quickly checked for authenticity by viewing under a UV light. UV invisible fluorescent inks cannot be reproduced on a scanner or copier. This ink is available for wet or dry offset, flexographic and gravure printing.

There are many types of ink being manufactured today.. Security ink is used for printing on passports, checks, some secure documents, and security labels just to name a few applications. There are several different types of security ink available for these applications that the following will cover.

Security Inks
  1. Biometric – Biometric, as its name implies, contains DNA tags. Special machines are designed that can read the tags, or the tags can be manufactured to react when a particular solvent comes in contact with them. Biometric ink is suited for applications where authentic product verification is necessary. Special methods are used to validate the authenticity of biometric ink printed products.
  2. Reactive – Reactive ink is also referred to as solvent sensitive. This type of ink can detect when there is an attempt to alter the document. An example of reactive ink is found on checks where variable data is printed on them. Watermarks are created with reactive ink.
  3. Optically Variable – Optically variable ink is also known as OVI in industry circles. Tiny flecks of metallic film that changes color when viewed from different angles. It’s somewhat like holograms. OVI ink is extremely expensive and must be printed in heavy weight. It’s used for passports and currency, for example. Color variations can include changing from brown to green then green to brown, or red to purple then purple to red respectively.
  4. Secondary Fluorescing – Fluorescing is an ink that becomes visible when it’s exposed to UV light. Like reactive ink, it’s purpose to detect alterations and tampering on the material upon which it’s used. For instance, the secondary fluorescing ink will look green under UV light, but turns red (the secondary color) if tampering has occurred.
  5. Thermochromic – As the name implies, thermochromic ink is designed to be sensitive to temperature. It will appear or disappear when it’s exposed to different temperatures. While it comes in a variety of temperature sensitivities, but the most common are 15.the most common are 15.31, and 45 degrees Celsius. Before using this industrial ink, it’s vital to consider the temperature conditions to which it will be exposed from the time of imprinting through its lifecycle.
  6. Invisible – Invisible ink is used to protect documents like checks. This type of ink is designed to be invisible to the naked eye, but visible under ultraviolet light much like fluorescing ink. Black light is the most common light source for making invisible ink visible.
  7. Magnetic – Magnetic ink is used where numerical sequences or serial number security is important. Magnetic ink contains magnetic flakes designed to communicate with electronic readers for document verification. It’s another ink used for checks MICR numbers in the UK. That MICR number holds highly sensitive data like check number, account number, and sort code.
  8. Water-Based Fugitive – Fugitive ink sounds mysterious, but it is designed to react much the same way as reactive ink. When an alteration attempt is made on a document with fugitive ink using any kind of liquid, including water, the ink will run, causing it to smudge and become unreadable. Even your finger with saliva on it will affect the printed background of a check or document with fugitive ink on it.

DNS’s principal objective is to provide our customers with the highest level of document protection available in the market.

Security inks are just one of the vital components that can be added to the production process.

Security inks have improved considerably over recent years and differ significantly to standard inks due to the wide range available and the complexity of the products.DNS have developed the necessary skills in utilizing specialist inks to deliver high quality secure products across various sectors.

Different considerations are required when trying to safeguard a document and today’s inks have advanced to reflect an ever changing market.It is very important to verify the target authentication method.How is the product checked – overtly or covertly?

Visual effects such as fluorescent and heat reactive inks are notable methods for instant verification of authenticity, alongside concealed features for covert detection are both crucial when protecting against fraud and counterfeiting.   

there are different type of inks as bellow:

Tamper evident

Where there is a concern that fraudsters are likely to alter or tamper with your document, there are measures that we can put in place to help identify that interference has occurred.A diverse range of tamper evident inks are available to aid detection when a document is susceptible to fraud.

Solvent Sensitive ink has been devised to identify when there has been an attempt to remove or amend printed data from items such as cheques or tickets. The ink will smear or change colour when exposed to solvents. This will ordinarily be applied on printed watermarks and fine line designs.

Adhesion Promoting Varnish can be applied to documents that have an element of personalisation printed. The purpose of the varnish is as the name suggests is to aid the adhesion of toner to the substrate. Another feature of this product is that it can only be viewed using a UV light and if the toner has been removed or altered there is an apparent colour difference.

Fugitive inks (aqua) have been developed to protect products against fraudsters trying to tamper with documents with the use of water or water based solutions. Any bid to remove with water will cause this ink to run or blot giving anyone who is verifying a chance of identifying a forgery. There is also availability of a solvent sensitive & water sensitive ink that combines both ink characteristics.


An ink which contains crystals of rare-earth metals (ytterbium, thulium, etc.) and glows when exposed to IR light of high intensity. Luminophores which glow green are the most commonly used.

Security features printed using inks with anti-Stokes properties, often referred to as up-converting inks, are invisible to the naked eye and can only be visualised under high intensity IR illumination that causes them to emit a visible colour emission.

Used on a variety of high security documents including high denomination banknotes, travels documents and pharmaceutical labels, anti-Stokes security inks are manufactured using luminsecent materials containing rare-earth metals.

Blind Inks

Blind inks are inks which have visually the same red colour, but one of those two inks will appear under a red filter, whilst the second one will disappear.

This is used for obtaining the apparition on a text and to establish its authenticity.

On the left side: with the red filter. On the right side, without the red filter.

Numbering inks

Numbering inks are mainly used by letterpress for the numbering of various security documents. Consequently their viscosity is suitable for this type of printing process.

They all have a verygood light fastnes of 7 on the blue wool scale.

In addition to their visible colours, they can be:

– fluorescent in green, yellow, or red

– migranting in red or pink

– they can be used on papers of 90gsm maximum, but not a coated paper, nor on plastic, nor on metallised supports.

Bip-Pen inks

This family of inks, always of black colour, is used for printing security documents.

By using specific pigments which give a conductiblilty to those inks, and therefore to the printed area, authentification of the document is made by using a special Bip-Pen which will emit immediately a green light if the document is the original, or a red light if the document is not the oiriginal. The Bip-Pen is sold by Petrel.

Those inks can be printed in offset, water-based or solvent based flexography, solvent-based silk-screen, and have only a black colour.

Coin reveal-able inks

Coin revealble inks are often used in security for obtaining the apparition of a hidden message on the original document, and sometimes in Direct marketing.

After printing and drying, this ink is totally invisible, but it is revealed by using a simple coin, (preferably made of copper or brass) rubbed on the printed area. Then the print will appear irreversibly in grey.

Coin revealable inks exist for offset, letterpress and flexography.