The slogan “banknote security hangs by a thread” is used by the paper subsidiary Louisenthal of the German printer Giesecke+Devrient to emphasize that banknote security is not as simple as one might think.
The company mentions in its July newsletter that nothing like a watermark carries the burden of security, but in a well-designed banknote, many features must come together optimally.
He explains that safety devices must work in a wide range of conditions, “not just in a laboratory, but in the evening in a restaurant, in a bar, at sunset or in direct sunlight”. Something may look great in a well-lit meeting room, but in less than ideal lighting conditions or when it’s bent and crumpled, it becomes problematic. Additionally, the security features should be visible in a range of environments and on different denominations, while contributing to the aesthetics of the banknote.
Part of the answer lies in the work done at Louisenthal to make security threads more attractive and technically advanced. The width of the threads increases. Not only is it more appealing to the eye, but the wires themselves can have more security features.
One of them is called MultiCode, an exclusive magnetic coding authentication technology, in which the code embedded in the security thread of a banknote can be personalized. Louisenthal calls his innovation “ingenious,” in that it allows the issuer to store information about the banknote’s denomination, country, and other specified information. He explains that the details of how these codes are made are not publicly available and that it is almost impossible for counterfeiters to copy the technology. It is embedded during the yarn production process and should last the lifetime of the banknote.
Incorporating a wire into a note isn’t as simple as it sounds, as early experiences with the US Federal Reserve’s latest $100 note show. Louisenthal says: “Security threads must also be firmly attached to the paper, and it must not be possible to tear them. This is a challenge because the art of papermaking is to create something as ‘pure’ as possible, but security threads involve introducing a deliberately disruptive element.
Factors to consider with new technologies, beyond printing, watermarks and ink, include questions about what temperatures the heat seal adhesive can tolerate and how an adhesive can be prevented to tarnish the other effects of the note.