Foil - The Ultimate Answer

Ever since they first appeared on banknotes in 1988, security foils in general, and the KINEGRAM in particular, have become a predominant security feature. They take a prominent place in surveys regarding the public's knowledge and expectation of security features: Second only to watermarks, and with significant distance ahead of the runners-up, foil-based security features are the most widely remembered and expected security features for the general public.

Also, foil is a standout performer when people's ability to use different security features for counterfeit recognition is tested. It is therefore not surprising that especially in recent times, where the issuing of new banknotes attracts ever higher levels of attention, many central banks have opted for foil to secure their new banknotes or banknote series against counterfeiting. Besides providing superior levels of security, these foil-based optically variable devices (OVDs) also play a major role in the banknote design.

Within the banknote industry, expectations are very high regarding the aesthetic quality of new banknotes - and the use and clever integration of innovative Level 1 security features. Banknote designers need to be familiar with the characteristics of these features so as to achieve a successful overall design composition, utilising the best and latest security technology. At the same time, we know that people's awareness of security features has a direct influence on their confidence in the note. So in order to maximize the security of a currency, it is paramount to employ features which are easily noticed, user-friendly and self-explanatory - because the features will only work and provide security if they are actually noticed by the general public.

It has been confirmed, in many recent studies on the use and perception of banknotes and security features, that:

1. People tend to look at and remember an average of 2.5 security elements.

2. Both the banknotes and their security elements should be bright, colourful, with a clearly visible key motif, and clear optical effects which are interesting to explore.

3. Besides being attractive and visually dominant, these features should also be easy to use.

The immediate conclusions that can be drawn from these findings are clear:

1. If the public only remembers about two to three features, designers are well advised to include such features in their portfolios which are versatile and flexible, and can easily work in various design concepts.

2. If security features need to be bright and interesting to explore, and deploy a clear visual expression, it is necessary to know the look and type of optical effects which are achievable with different features.

3. If these elements must be easy to use, this ease and simplicity should also apply to their ease of use in banknote production, and their durability in circulation.

In some cases, banknote designers may have been misled into thinking that foil-based OVDs would not be an obvious or easy-to-integrate part of banknote design. However, the contrary is true - foil is a prime security feature, and not a standalone one. In the following, we will look at how it is ideally suited for a multitude of purposes and can very effectively solve multiple design challenges.

1. Versatility of foil features

Working with Windows

Windows are one of the latest trends in securing banknotes, to which a designer has to respond. Using foil allows windows to work most effectively, and add security, for polymer, composite, and paper-substrate notes. In the latter case, foil also seals and protects the window. Sophisticated foil features are able to offer clear and distinctive diffractive effects, and are not restricted to the window areas only. With a foil solution such as KINEGRAM REVIEW, which shows different diffractive images for front and back sides of the banknote, as in the new 20, and soon in the new 50 Euro, the window-in-banknote technology multiplies designers' opportunities for using the foil to connect the banknote's recto and verso and to offer two entirely different optical images to the public, which they can use for authentication. In addition, the foil even works as a transmission feature.

Creating Empathy

It is desirable to create strong emotional responses and empathy among the public. Faces and eyes are very well suited to achieve this, especially when it comes to portraits of famous persons. It is well known in banknote design that portraits are very popular among the public because of their recognisability, so using portraits to catch attention and trigger authentication is quite natural. For the banknote user, it is a self explanatory way of checking your banknotes. There is a range of different solutions for including portraits in foil, for example as a greyscale portrait, a true-color portrait, or a 3D optical illusion as depicted in the image below. An innovative solution is to have the watermark, the intaglio and the foil all work with the same portrait in three different technologies, making it very easy for the public to identify the note as genuine.

Depiction of realistic images

Realistic images receive more attention than abstract ones. People's eyes tend to linger on realistic images for a longer time. Therefore, it should be a design principle to create realistic images true to detail. The foil patches on Denmark's banknote series are a beautiful example of depicting real objects in a security feature. They show archaeological artefacts of Denmark's rich, centuries-old history, for example the "Sun Chariot" on the 1,000 Kroner banknote. While the banknotes in themselves are rather reduced in their design, the patches, with their realistic images of archaeological items, bring them to life, creating interest and catching the attention of the viewer.

Use of color

Color is another, very effective way of leading the human eye to a security feature. It is also the visual component that people remember most about objects and thus will result in more attention and better memorization by the banknote user. A very recent technological invention, KINEGRAM COLORS, now allows banknote designers to integrate the print design colors in foil. Different diffractive elements can be realized in different colors within one foil feature. This helps to increase the prominence and attractiveness of the foil and significantly improves the possibility to integrate it into the overall banknote design. Available also as a solution for window banknotes, the colors for both front and reverse of the banknote can be freely chosen; even multicolored patterns are possible.

This is a major step towards integration with the banknote print in both motif and colors, in two ways: elements and colors from the printed banknote design can be repeated or echoed in the design of the foil; or the foil can even complete the banknote's print motif. In both cases, the interaction between foil and print enhances the note's visual attractiveness and anti-counterfeiting security. The Bank of England has decided to use this technology, a world first, in their new 5 Pound banknote which was issued on 13 September. The note has a multi-colored foil stripe with gold and silver on the front and silver and green on the reverse.

Overprinting of features

Speaking of print integration, in some cases it will be desirable to overprint a surface-applied security feature, which also enhances the banknote security. This is made extremely easy with foil, which can of course be overprinted with offset, as is done for example on the new 5 and 10 Euro notes, or with intaglio. Moreover, foil can also be overprinted with silkscreen, and even be varnished.

2. Optical Effects


Catching the viewer's attention is made very easy by using movement. Prominent and clear, distinct movements are a very obvious and easy-to-understand optical effect. The vector-based KINEGRAM technology allows the designer to manage light precisely so as to achieve distinct movement effects in foil, where one fine line will light up after the next in a fluid but clearly discernible motion. In similar fashion, transformation or morphing effects display one image morphing into another through a discrete number of clearly distinguishable steps. Such an effect is a very high barrier to counterfeiters. The same is true for dynamic movement effects, where different areas of a design appear to move in opposite directions at the same time.

3D Illusions

Foil can create 3D optical illusions, which are an obvious naked-eye security feature whereby a flat image appears to protrude from the surface of the banknote. The banknote user is prompted to touch the feature, notice that it is not embossed but just an optical illusion, and thus verify that the banknote he holds in his hand is genuine. This effect is especially suitable for simple symbols or denomination numerals.

Color Shift Effects

Foil features also allow color shift effects, for example based on thin-film technology. The combination of this with the multitude of other visual effects that a foil can have, creates added security value - and can be very helpful for a banknote designer where he or she is confronted with space or cost issues in the choice of security features. By adding a color shift to a security foil, the best of both worlds can be combined in a single feature.

Size of Optical Effects

The size of security features also matters. Large features will be more easily perceived than smaller ones. For this reason, the multiple patch concept for registered foil stripes has been created. This is a modular concept allowing the use of several different optical elements, and visual effects, in one foil feature, which will appear in the same height and position on every note. It is possible to design fully separate, clearly identifiable and distinguishable elements, and therefore a selection of different optical security technologies, within one foil stripe. This not only will leave a choice of which one to focus on for the banknote user, but also the design elements can be larger and thus more easily recognizable.

3. Ease of Use - Technology, Production and Durability

In principle, foil offers virtually endless possibilities to comply with the technical profiles of different banknote printers.

Foil features can be designed onto any substrate - be it polymer, the different types of composite substrates, or paper. Foil features can be designed for any application format - as a patch, a multiple patch, a patch over windows, a stripe, a registered stripe, or a registered stripe over window areas.

Foil features can be designed in virtually any shape, due to the possibilities offered by different partial metallization techniques. Notably, the extremely fine partial metallization technique known as KINEGRAM ZERO.ZERO offers unprecedented design flexibility and unparalleled possibilities for print integration. The line resolution can go down to 3-5 microns, invisible to the naked eye.

Finally, as discussed above, foil features can now also be designed with a multitude of different colors, which are in perfect register to the partial metallization. Foil is also very versatile when it comes to actual banknote production. Even the complex new developments and the most sophisticated foils can be applied using existing equipment and existing machines, and at different stages in the banknote production process.This will give a banknote designer enormous flexibility, and reassure her that when designing a foil, this will not create any technical issues in banknote production.

Foil can be applied either in the paper mill, i.e. at the substrate manufacturing stage, or at the banknote print works, as one step in between printing processes. In the print works, both patch and stripe formats can be processed, and the foil can either be applied before, or on top of, the offset print. The latter case allows an interaction between the foil and the print, which will be visible in the transparent, non-metallized areas. In this regard, the inevitable positional tolerances of foil are at least as good as, or even better than, the tolerances of printing processes to each other.

In terms of durability, the multitude of foil features in use around the world, in the most varied climatic and circulation conditions, demonstrate the excellent durability of foil. In fact, the chemical formulation of foil features is individually engineered to match the specific durability requirements of each project. Foil has been known to surpass all durability tests set by leading central banks.


When creating a note, it is highly recommended that banknote designers get in touch with the foil producers, in order to turn their ideas into a functional and highly secure foil feature. Foil offers enormous potential - and may well be the ultimate solution when deciding on a principal security feature for upgraded or new banknote designs.

Versatility and Flexibility - Well designed and integrated foil security features will be remembered easily, and its adaptability to the most varied design concepts makes foil an ideal feature.

Optical effects - Foil can be designed in a multitude of different ways and offers an unparalleled visual expression with diverse optical effects. It can be bright, colourful, and interesting, and easily ties in with the overall banknote design composition.

Ease of use - Foil offers enormous technical flexibility and responds to virtually any given technical manufacturing framework. Its ease of use in banknote production and durability in circulation are proven around the world, making it the feature of choice in innovative banknote design and for leading issuing authorities.

The best results are always achieved through close collaboration between banknote designers, the foil producer, and the central bank customers. With ideas and dedication coming from all these stakeholders, the chances are high that the resulting banknote will be perceptually effective, easy to use and communicate, and a beautiful calling-card for the issuing authority.


KINEGRAM, KINEGRAM COLORS, KINEGRAM REVIEW and KINEGRAM ZERO.ZERO are registered trademarks of OVD Kinegram AG, a member of the KURZ Group.  

This article was published in "IBDA Insight" Magazine, Vol. 12, November 2016.