When dealing with federal, private or classified documents, security measures are often taken to thwart the efforts of counterfeiters. There are a wide variety of technologies that can be employed in a security application.
Security Printing Techniques
Intaglio printing
Intaglio has always been the effective choice as a principal security feature for bank notes since it offers razor sharp imagery which difficult to imitate by other means.
First the image area is engraved onto the surface of the platem then the surface is covered in ink, and then rubbed vigorously with a cloth or newspaper to remove 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 press, transferring the ink to the paper.
Artistic Screening
In traditional printing, halftone dots are most commonly used to create the illusion of gradients and tones. Artistic screening takes this idea a step further and instead of using dots as a halftone, graphics and even text can be used to build the image.
An excellent movie illustrating this process can be found here.
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.
Guilloché Patterns
Guilloché patterns are spirograph-like curves that frame a curve within an inner and outer envelope curve. They are used on banknotes, securities, and passports worldwide for added security against counterfeiting. The figures below show the same guilloche pattern plotted by various mathematical equations.
Guilloché machines (also called geometric lathes) consist of many gears and settings that can produce an infinite number of patterns.
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 undiscernable to the naked eye. Cheques, for example, use microprint as the signature line.
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.
Holograms
A hologram may be embedded either via holographic paper, or onto the laminate of a card itself.
RFID
With the advent of RFID, it is possible to insert extremely small RF-active devices into the printed product.
Consecutive numbering changes sequentially from one document to the next. It can be used as a control feature to provide a distinct identity to each document. The standard numbering color is red, but other colors are available. Alphabetic characters can also be included in the number.
Sequential Numbering
Number Orientation
A consecutive number can be printed in almost any location on a document. The number can be printed parallel or perpendicular to the rest of the copy on the document and multiple numbers can also be printed. It is best to consult with your print supplier for their capabilities as this may differ between suppliers.
Bar Code Numbering
Bar code numbering is used on many types of applications to code and decode information automatically. It consists of bars and spaces of various sizes as shown in the sample above. The bar codes can be static (the same number on each piece) or consecutive (sequential from piece to piece).
A number of different types of bar codes have been developed to meet the special needs of different industries. The different bar code types are known as symbologies. The scanned information is received without the input errors that can occur with the use of traditional methods of entering data.
Mod Numbering
MOD (Modulus) or check digit numbering involves printing an additional digit to the right of a base sequential number (as indicated by the black digit in the numbers shown below).
This enables the document owner to verify and control some aspect of the document; it’s contents, or the intended end-user of the document. Numbering methods, such as MICR, Gothic, OCR, or Bar Code, can be to be used.
Numbering Security Features
A number of features can be incorporated with numbering to provide security to documents. Two of the most popular are Rainbow numbering and Bleed-through numbering.
- Rainbow numbering: A special technique that gives the number a rainbow appearance.
- Bleed-through numbering: A technique in which the numbering ink contains a pink dye that
Security Paper
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.
This is accomplished by impressing a water coated stamp 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.
Security Threads
There are two kinds of security threads. One is a thin aluminum coated and partly demetalized Polyester film thread with Micro printing 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.
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 cheques will display the word “VOID” (or the equivalent in another language) on the copy, even though it is absent from the original.
Security Inks
OVI
OVI (Optically Variable Inks) change color when viewed at different angles. 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. Currently there are only two types, green to purple and gold to green.
Magnetic ink
Because of the difficulties in forging magnetic ink characters, and 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.
Fluorescent dyes
Many banknotes incorporate dyes which fluoresce under ultraviolet light. These show up as words, patterns or pictures under a UV light source.
This feature is also incorporated into other documents – anything from prescriptions, to identification forms and savings bonds have used flourescent inks successfully.
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