The last decade has seen a massive emergence of windows in banknotes throughout the world. Transparent, translucent, with transforming or hologram images, and serving as filters, all these security features are constantly under scrutiny by Regula’s experts.
The Regula team never stops following and analyzing existing and novel security features in all kinds of identity and security documents. We have registered various types of windows in the notes of European countries, Asian states, Australia, the Middle East, and Latin America.
Let's zoom in to reveal how to tell if money is fake by looking through secure windows.
What is the window on money for?
Nowadays, a window in a banknote is an established and reliable security feature that is almost impossible to counterfeit. It’s eye-catching, easily recognizable, and can be checked for authenticity both with and without special equipment.
Banknotes with windows may start as a clear sheet of plastic onto which several layers of ink are applied. Windows are made by leaving some sections of plastic free of ink. However, a polymer sheet that forms the core of a banknote may be covered with paper on both sides. In this case, a window is made in the outer layers of paper. It is cut out, which makes the plastic visible. Paper notes can also contain secure windows, and they are usually generated either at the sheet-making stage or are formed by a laser and then filled with some transparent film (using liquid crystals or nanomaterials, for instance).
After being created, see-through windows can be left as they are, or they may be framed or covered with some images, vignettes, embossing, metallized coating, etc. Not only do all these elements make transparent windows look fancy and captivate viewers, but contribute to banknote security.
Insights into banknote security technology: Types of secure windows
To authenticate a window and all the elements it might contain, a person needs to look at it directly, rotate the note to see the window at another angle, hold it up to the light, and view on a different background (light or dark).
Let’s have a closer look.
Some windows serve as filters – they reveal hidden images, texts or codes printed on the same banknote. To witness this effect, one needs to fold the note so that the window is placed above the area where something is encoded. Like in a Brazilian real, for example:
Another wow effect is shown in a secure window that contains a diffractive optical element (DOE) – a so-called winDOE. It visualizes a rainbow hologram image when seen in transmitted light from a point light source (lamp, flashlight, etc.). To get the point, let’s examine a Romanian leu:
However, not all secure windows are transparent. In some cases, only one side of a polymer substrate of a banknote is left visible, while the other side is opacified. This is known as a half window. It’s glossy where it shows, and the rear side of a note serves as a regular printing surface.
How to authenticate secure windows in banknotes
Indeed, examining windows in banknotes can be rather amusing, and anyone can easily see all the tricks with their own eyes. Nevertheless, using special equipment can add to the verification of windows and thus to the authentication of banknotes.
For example, magnification with special devices will show whether the framework of a secure window is cut correctly. It will also allow you to define the method of printing for a vignette. If a window is created by a laser, magnification will reveal that its edges are correspondingly burnt. So, even if malefactors somehow try to counterfeit a banknote with a secure window (which is really hard; for example, Australia has not yet come across a single attempt at falsification of such banknotes), forensic devices will show it immediately.
Regula’s solutions for banknote security feature verification
Regula’s latest compact device – Regula 1031 – allows for 24x magnification, and this significantly helps to thoroughly examine the security features of any banknote, as well as any identity document. And the spectral comparator Regula 4308 and its polarizing filter can help verify the presence of liquid crystals in the film that forms a window in a note.
All the knowledge and data on various security features in documents, accumulated by the experts at Regula over more than 30 years in the industry, have translated into robust Information Reference Systems that assist in the authentication process at border control points, in currency exchange offices, etc. These systems provide databases of travel documents, banknotes, driver’s licenses, and vehicle registration certificates with a detailed description of their security features.
The Currency Information Reference System contains data on 200 currencies that are arranged by country and production series. Overall, the database numbers over 7,300 banknotes and coins.
To learn more about various banknote security features, please check Regula’s extensive glossary, which describes them all.