Security printing
Security printing is the field of the printing industry that deals with the printing of items such as banknotes, passports, tamper-evident labels, product authentication, stock certificates, postage stamps and identity cards. The main goal of security printing is to prevent forgery, tampering, or counterfeiting.
A number of technical methods are used in the security printing industry.
Special paper
Most banknotes are made of heavy paper, almost always from cotton fibres for strength and durability, in some cases linen or speciality coloured or forensic fibres are added to give the paper added individuality and protect against counterfeiting. Some countries including Romania, Mexico, New Zealand, Israel, Singapore and Australia produce banknotes made from polymer, in order to improve wear and tear, and permit the inclusion of a small transparent window a few millimeters in size as a security feature that is very difficult to reproduce using common counterfeiting techniques.
Watermarks
A watermark is a recognizable image or pattern in paper that appears lighter or darker than surrounding paper when viewed with a light from behind the paper, due to paper density variations. A watermark is made by impressing a water coated metal stamp or dandy roll onto the paper during manufacturing. Watermarks were first introduced in Bologna, Italy in 1282; as well as their use in security printing, they have also been used by papermakers to identify their product. Watermarks can also be made on polymer currency, for example, Australia has its coat of arms watermarked on all its plastic bills.
Intaglio printing
Intaglio is a printing technique in which the image is incised into a surface. Normally, copper or zinc plates are used, and the incisions are created by etching or engraving the image, but one may also use mezzotint. In printing, the surface is covered in ink, and then rubbed vigorously with tarlatan cloth or newspaper to remove the ink from the surface, leaving it in the incisions. A damp piece of paper is placed on top, and the plate and paper are run through a printing press that, through pressure, transfers the ink to the paper.
The very sharp printing obtained from the intaglio process is hard to imitate by other means. Intaglio also allows for the creation of latent images which are only visible when the document is viewed at a very shallow angle.
Geometric lathe work
A guilloché is an ornamental pattern formed of two or more curved bands that interlace to repeat a circular design. They are made with a geometric lathe.
Microprinting
This involves the use of extremely small text, and is most often used on currency and bank checks. The text is generally small enough to be indiscernible to the naked eye. Cheques, for example, use microprint as the signature line.
Optically Variable Color-changing inks
Color changing inks are inks containing pearlescent pigments that change color when viewed at a different angle. The color of the ink does not actually change, but the angle of the light to the viewer's eye changes and thus creates the change in color. A number of types are available, including green to purple, gold to green and green to lilac.
Holograms
A hologram may be embedded either via hot-stamping foil, wherein an extremely thin layer of only a few microns of depth is bonded into the paper or a plastic substrate by means of a hot-melt adhesive (called a size coat) and heat from a metal die, or it may be directly embossed as holographic paper, or onto the laminate of a card itself.
Security threads
There are two kinds of security threads. One is a thin aluminum coated and partly demetalized polyester film thread with microprinting which is embedded in the security paper as banknote or passport paper.
The other kind of security thread is the single or multicolor sewing thread made from cotton or synthetic fibers, mostly UV fluorescent, for the bookbinding of passport booklets.
Magnetic ink
Because of the speed with which they can be read by computer systems, magnetic ink character recognition is used extensively in banking, primarily for personal checks. The ink used in Magnetic Ink Character Recognition (MICR) technology is also used to greatly reduce errors in automated (or computerized) reading.
Some people believe that the magnetic ink was intended as a fraud prevention concept, yet the original intent was to have a non-optical technology so that writing on the cheque, like signatures, would not interfere with reading. The main magnetic fonts (E13-B and CMC7) are downloadable for a small fee and in addition magnetic toner is available for many printers. Some higher resolution toners have sufficient magnetic properties for magnetic reading to be successful without special toner.
Serial numbers
Serial numbers are not difficult to forge, but make legitimate documents easier to track and audit.
Anti-copying marks
In the late twentieth century advances in computer and photocopy technology made it possible for people without sophisticated training to easily copy currency. In an attempt to prevent this, banks have sought to add filtering features to the software and hardware available to the public that senses features of currency, and then locks out the reproduction of any material with these marks. One known example of such a system is the EURion constellation.
Copy-evident paper
Many secure documents have the feature which causes a photocopy of the document to appear obviously different from the original. For example, when photocopied, most checks will display the word "VOID" (or the equivalent in another language) on the copy, even though it is absent from the original.
Fluorescent dyes are dyes which fluoresce under ultraviolet light or other unusual lighting. These show up as words, patterns or pictures and may be visible or invisible under normal lighting. This feature is also incorporated into many banknotes and other documents - e.g. Northern Ireland NHS prescriptions show a picture of local '8th wonder' the Giant's Causeway in UV light. Some producers include multi-frequency fluorescence, such that different elements fluoresce under specific frequencies of light.
Registration of features on both sides
Banknotes are typically printed with fine alignment between the printing on each side of the note. This allows the note to be examined for this feature, and provides opportunities to unambiguously align other features of the note to the printing. Again, this is difficult to imitate accurately enough in most print shops.
Electronic devices
With the advent of RFID, it is possible to insert extremely small RF-active devices into the printed product to enhance document security. This is most apparent in modern biometric passports, where an RFID chip mirrors the printed information.
Thermochromatic ink
Security ink with a normal "trigger" temperature of 88 degrees F, which will either disappear or change colors when the ink is rubbed, usually by the fingertips.
Latent Images
Pressure sensitive or hot stamped labels characterized with a normal (gray or colored) appearance. When viewed via a special filter (such as a polarizer) an additional, normally latent, image appears.
See also
External links
- SRI Specialty Materials- Security Inks
- Security Printing Conference by Pira International
- Delina Security Design (www.eradinamika.co.id)
- Security Printing and Design software (www.guard-soft.com)
- The council of the EU: Glossary of Security Documents, Security Features and other related technical terms
- TorApp.Info Online Security Printing and Design platform