FDE 101: Mechanical Printing Processes Expert Overview

No security document is 100% counterfeit proof, and in some cases, even poor quality, digitally simulated documents can pass as genuine to an untrained eye. There are several methods to deter criminals from creating convincing counterfeits. A key strategy involves using a mix of different printing processes and strategically integrating security features so that these elements work together effectively.

An understanding of the printing processes used to create documents is essential for properly examining their authenticity.

Forensic Document Examination 101: Mechanical Printing Processes

Forensic document examiners (FDEs) possess knowledge about the manufacturing of security documents and are trained to recognize subtle details in various printing methods and security features.

An FDE will utilize appropriate magnification and may employ varied lighting conditions as needed, including oblique, ultraviolet, infrared, or transmitted light.

If the examiner observes a combination of printing process characteristics and security features in the genuine specimen document that conform to those in the questioned document, they are more likely to conclude that the questioned document is genuine.

If the opposite is true, it is more likely than not that the questioned document is counterfeit. Occasionally, defects may arise during the manufacturing process, and a trained FDE can distinguish between a defective document and a counterfeit one.

Types of Printing Processes

All photo examples are copyright of the Council of The European Union, Public Register of Authentic Travel and Identity Documents Online, PRADO.

Letterpress is a typographic process that uses a printing plate with a raised surface, which is coated with ink, as illustrated in Figure 1. This printing process is primarily employed for producing paper items that need serialization, such as currency, passports, visas, and social security cards. The printing plate is pressed onto the paper with a moderate amount of pressure, transferring the inked image onto the paper substrate

^{Fig. 1}

Letterpress printing is characterized by three key features:

1. The printing plate creates an embossing effect on the paper.
2. Excess ink that cannot be absorbed by the embossed areas is squeezed out around the edges of the printed material, resulting in what is known as the “halo effect.”
3. There can be void areas within the printed image where no ink is transferred (though these are not shown in the illustration).

Over time, the materials used for plates have evolved from wood to metal and now to photopolymers. Each material, combined with the hardness or softness of the paper, affects the level of embossing and the characteristics of the “halo effect.”

Flexography can be thought of as a sub-category of letterpress. It is a typographic process that involves a printing plate with a raised surface covered with ink as illustrated in Figure 2. Similar to letterpress, most printing plates are currently made from photo-polymeric materials and use minimal impact to transfer images onto the object’s surface.

Flexography is distinct from letterpress printing because it operates on the cylindrical surface of a rotary press. In the flexographic printing process, the materials used for printing can include paper, polyethylene, various plastic-like substances, and different types of foils. 

One of the key features of flexographic printing is its sharper line definition compared to letterpress. Additionally, it creates a “halo effect,” although it typically does not produce embossing

^Fig. 2

Flexography has been used to print on:

• government identification cards
• foil
• plastic film
• corrugated board
• paper
• paperboard
• cellophane
• fabric

Offset lithography involves the use of printing plates without the impact like letterpress as illustrated in Figure 3. It is a planographic process, meaning the printing happens along a linear plane.

In a basic offset system, the paper to be printed upon passes between two cylinders. The cylinder on top, called the blanket cylinder, rolls across the substrate, and transfers an inked impression to that substrate. The cylinder on the bottom supports the substrate as it passes through the blanket cylinder.

^{Fig. 3}

Offset is used extensively for printing on:

• packaging
• newspapers
• magazines
• credit cards
• driver licenses
• birth certificates
• passports
• currency

Intaglio is a printing process by which the image to be printed is recessed into a printing plate as illustrated in Figure 4. The recessed area is filled with ink and is pressed into the substrate with extreme pressure, transferring the ink from the plate to the substrate.

^{Fig. 4}

Characteristics of intaglio printing include a raised surface and a “feathering” or “bleeding” effect at the edges of the printed material.

Intaglio printing is used on:

• currency
• passports
• birth certificates
• automobile titles
• wedding invitations
• business cards

Screen-process printing involves forcing ink through a mesh material (normally woven synthetic material or steel) that is attached to a frame as illustrated in Figure 5. Masking material is used to selectively block out areas of the screen to form the image to be printed.

^{Fig. 5}

Screen printing is used on security documents but also on mediums such as posters, art prints, textiles, label printing, bottles, or other odd shapes.

Questioned Document Examinations

Questioned document examination is a discipline within forensic science that pertains to documents with disputed authenticity or origin. A questioned document investigation is used to ascertain the authenticity (or lack thereof) of a document when it comes into question. The examination of known to questioned documents provides analytical results regarding the similarities or differences between the documents using a scientific principles, methods, and equipment in which Forensic Document Examiners are trained.

To discuss your case with an expert, call us at 800.813.6736 or submit an inquiry.

Source

Council of the European Union, Public Register of Authentic Travel and Identity Documents Online, PRADO, “Glossary, Technical Terms Related to Security Features and to Security Documents in General.”  (Brussels, Belgium: European Union, 2022) https://www.consilium.europa.eu/prado/en/prado-glossary/prado-glossary.pdf (accessed October 24, 2022).

Featured Expert

Traci L. Moran, M.F.S.

Forensic Document Examiner

Traci Moran is a Forensic Document Examiner (FDE) with 30 years of professional experience in government agency work. Traci provides examinations, reports, and testimony toward the resolution of… read more.