Joel Zlotnick, Traci Moran and Tyra McConnell
Counterfeit Deterrence Laboratory
Office of Fraud Prevention Programmes
Bureau of Consular Affairs
US Department of State

Security fibres and planchettes are among the oldest anti-counterfeiting technologies used in paper security documents, but modern innovations provide an abundance of design and technology alternatives.

Some considerations for security fibre implementation include which security fibres best resist simulation, how fibre types can be combined for a distinctive document-specific substrate, and how security fibre inspection can be facilitated for document end users. 

Though watermarks and security threads are also important contributors to substrate security, the scope of this article is limited to design and technology alternatives for security fibres. 

Describing security fibre characteristics
When a security document is described in user training materials, security fibres are typically characterised by their visible or ultraviolet (UV) colours, with little mention of other characteristics. 

For example, the security substrate in Figure 1 might be described as containing red, blue and yellow security fibres, maybe with a note that the yellow security fibres also glow yellow in UV light. But some types of innovative security fibres can be described in more complex ways.

Figure 1: A security substrate in reflected light (left) and UV light (right). This substrate could be said to contain red, blue and yellow security fibres, where the yellow fibres also glow yellow in UV light, but colour alone does not encompass the full range characteristics that security fibres can exhibit.

For example, the security fibres in Figure 2 can be differentiated not only by colour, but also by shape. Multicolour fibres are also available in various shapes. 

Figure 2: Straight green security fibres (left) and a different security substrate containing wavy pink security fibres (right). These fibres can be differentiated not just by colour, but also by shape.

Figure 3 looks like two fibres joined lengthwise, where one half is pink with no UV response and the other half is yellow and glows yellow in UV. 

Figure 3: A two-colour double security fibre in oblique light (left) and UV light (right). Both pink and yellow can be seen on the left, but only the yellow half glows in UV light on the right.

Figure 4 looks like pink beads on a blue string in visible light, but a dotted red line in UV since only the intermittent pink areas glow. 

Figure 4: A two-colour security fibre in reflected light (left) and UV light (right). In visible light this fibre looks like a blue strand intermittently coated with pink material. In UV light, only the pink material glows, so it looks like a dotted line.

The wider security fibres in Figure 5 show two colours in visible light and four colours in UV light. 

Figure 5: Multicolour security fibres in oblique light (left) and UV light (right). Two colours are visible in each fibre in the image on the left, but the UV image on the right shows four different UV colour responses. The wide, straight shape of these fibres is also distinctive.

Similarly, the planchette centred in Figure 6 was punched from paper that itself contains red and blue fibres. 

Figure 6: Planchettes in reflected light (left) and UV light (right). The planchette in the centre was punched from a paper substrate that contained its own red and blue security fibres. The UV image shows the pink planchettes glowing orange, and invisible UV-reactive fibres throughout the sheet.

Note that the multiple visible and UV colours within each fibre in Figures 3 through 6 are always in perfect alignment with one another, and this has important security implications. 

Briefly, multicolour fibres can better resist certain security fibre simulation methods than monochromatic fibres, though a complete discussion of why exceeds the scope of this article. 

Combining fibre types in a security substrate
Highly proprietary security fibres deployed in only a single document are not common, except in the most demanding security document applications.

It is more typical for a particular security fibre to be incorporated into multiple security substrates. Yet a selection of different commercial security fibres, combined in a novel way, can create a substrate with a highly individualised security fibre profile. 

For example, Figure 7 shows visible red/blue multicolour fibres that also glow red and yellow in UV, and two invisible fibres that fluoresce red and yellow in UV, resulting in a fibre combination highly specific to this particular substrate and document. 

Figure 7: A red and blue striped fibre in reflected light (left) that also responds in UV light (right) and invisible fibres that fluoresce either red or green in UV (right). Even if these fibres were individually used in other security document substrates, this combination is specific to this substrate.

Fibres can also be combined with planchettes as in Figure 8, configured with different lengths for each fibre colour as in Figure 9, combined with UV-fluorescent particles as in Figure 10, or included in different ratios/quantities as in Figure 11. 

Figure 8: A security substrate in reflected light (left) and UV light (right). The UV image shows security fibres and planchettes combined in the same substrate.
Figure 9: A security substrate in reflected light (left) and UV light (right). The UV image shows fibres of different colours also customised with different lengths.
Figure 10: A security substrate in reflected light (left) and UV light (right). The tiny round particles visible in both images have been combined with visible security fibres (left).
Figure 11: A security substrate in reflected light (left) and UV light (right). There are many more pink fibres than blue or yellow fibres, so the ratio between different fibre colours can help differentiate this substrate from other substrates that may contain similar fibres but in different amounts.

Another strategy for individualising a substrate is clustering security fibres into a band instead of evenly throughout the sheet, as shown in Figure 12. 

Figure 12: A security substrate in reflected light (left) and UV light (right). The security fibres have been placed only within a narrow band instead of throughout the sheet, helping to differentiate this substrate from other substrates that may contain similar fibres spread evenly in the paper.

Each individual fibre or planchette type in Figures 7 through 12 may not be proprietary on its own, but each helps make the combinations unique.

While combining multiple security fibre types helps individualise and secure a substrate, too many different fibre types in a single substrate can confuse document end users. 

Finding the right balance between substrate complexity and manageable training is a matter for issuer discretion.

Security fibres and human factors
Some human factors related to security fibre inspection include visible and UV colour, fibre quantities and contrast. 

Some substrates contain only transparent fibres (with a UV response) and no visible fibres, like those shown in Figures 13. 

Figure 13: Colourless, nearly invisible security fibres in reflected light (left) and UV light (right). Invisible fibres may be less prone to interfere with document machine readability or quality control inspection processes, but invisible fibres are almost impossible for humans to inspect if no UV light is available.

Although this choice can be appropriate (if visible fibres interfere with machine readability, for example), such fibres are hard to locate or inspect if no UV light is available, or if the UV fluorescence itself is not bright and clear. 

Accordingly, issuers should consider including visible fibres if the document’s usage allows, with sufficient quantities of both visible and UV fibres to make each easy to find. 

A substrate with scarce fibres requires users to work harder to locate them and can easily be mistaken for a paper that does not contain security fibres at all.

For better contrast, document issuers should consider leaving some blank paper in designs because it is more difficult to see security fibres in paper covered with printed artwork, as shown in Figure 14. 

Figure 14: A security substrate in reflected light (left) and transmitted light (right). The blank paper in the left image is meant to alert users to the watermark in the right image, but areas of unprinted paper also help users locate security fibres more easily.

Further, contrast is improved when the fibre colours are sufficiently saturated to stand out against the substrate colour and different from ink colours used in document artwork. 

Contrast also extends to UV images. In Figure 15, the presence of the UV red colour in the security fibres in helps them stand out against the blue/yellow UV fluorescence of the security thread and UV artwork. 

Figure 15: A security substrate in reflected light (left) and UV light (right). The UV-reactive fibres in the right image are more easily spotted because the red fibre colour is not duplicated in the UV response of other security features, and because the UV artwork does not cover the entire substrate surface.

Further, because the UV artwork does not fully cover the document surface, contrast is improved and locating security fibres is easier in areas without multiple competing UV effects.

For many security features, including security fibres, design and ergonomic factors are as important as technology selection. Issuers may find the below ideas helpful when selecting and implementing security fibres in a document design.

  • Consider multicolour fibres, which can offer security advantages over monochromatic fibres
  • Consider visible fibres, since UV-only fibres are difficult to check if no UV light is available
  • Consider fibres that can be described by shape, size or other characteristics besides just colour
  • Consider combining fibres of different types to form a novel, document-specific combination
  • Consider leaving a region of unprinted paper to allow fibres to be located easily
  • Consider the contrast between visible fibre colour(s) and the colours of the document artwork
  • Consider the contrast between UV fibre colour(s) and the colours of other UV document features


Joel Zlotnick is employed by the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory as a physical scientist. He conducts research on how design strategies can help maximise the security value of printing technologies and security features, and develops training programmes on counterfeit detection.

Traci Moran is employed by the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory as a physical scientist. She conducts research on security documents and delivers counterfeit detection training to varied audiences.

Tyra McConnell is a Forensic Document Examiner at the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory. She provides training on security documents and develops presentations and e-learning courses regarding counterfeit detection.

Disclaimer: This document represents the opinions of its authors and not necessarily the opinions of the US government. The technologies and strategies described may not be available, appropriate or manufacturable for all document issuers. The examples shown do not imply anything about the quality of a document, its designer, its manufacturer, or the issuing authority. For informational purposes only.

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