Reddit users have been buzzing after a management employee discovered that shining ultraviolet light on Australian banknotes reveals hidden images of birds. The Reddit account C_Horse21 found a 100 AUD note and shared it online, quickly garnering over 2400 “upvotes” and sparking a flurry of comments.
Hidden features on Australian banknotes.
Each Australian banknote has three “invisible” features – a bird, the serial number, and the year of print – created using fluorescent ink. Each note features a different bird: the honeyeater (5 AUD note), the cockatoo (10 AUD note),, the kookaburra (20 AUD note), the black swan (50 AUD note), and the owl (100 AUD note).
While the hidden bird may have generated excitement and numerous conspiracy theories online, it is actually one of several unique security measures integrated into the currency design to combat counterfeiting.
Windows
The window feature on Australian banknotes also helps you determine if a note is ‘dirty’ or not.
The vertical window that runs down the middle of any banknote is a hallmark of Australian currency. However, many of the images contained in the window are not just decorative – they also help you determine if a note is ‘dirty’.
The star-shaped image at the top of the window will either protrude or recede when you tilt the note. An “angle test” can similarly be applied to the flying birds outlined in the window, which will flap their wings and change color as the note is moved.
The more detailed, colorful bird in the window will also change color when the note is viewed from different angles. A seven-pointed star at the bottom right of the banknote will also become clearly visible when held up to the light.
Numbers and Colors
The numbers on Australian banknotes will self-reflect when the note is moved, appearing both on the front and back depending on how the note is tilted. Another sign of a genuine banknote is the “rolling color effect,” with a kaleidoscope of colors visible within the bird located at the top left corner of the note.
This “color test” is also where the UV ink appears, with the “secret” bird discovered on Reddit being visible on real notes when placed under a UV light with a central wavelength of about 365nm.
