I’m doing a research project for a chemistry class and we need to create a brochure about how chemistry is used to battle counterfeit currency.
Chemistry is not my subject at all.
While I have most of the project done, can someone explain why, on Canadian banknotes, colour-shifting occurs? I’m referring to aspects like the feather on one bill going gold to green when moved up and down.
Thank you!
In: 2
This is called optically variable ink.
It changes the reflected wavelength of light when viewed at different angles. It’s paint with suspended particles that reflect differently at the viewing angles.
Part of it is chemistry though I think a good part of it is also physics, OVI’s are multiple layers of ink with particles that effectively bounce the light different. There are filter layers in between to cancel out/or change the different colors that appear. It’s not a perfect example but this [illusion with the transparent](https://www.youtube.com/watch?v=lvvcRdwNhGM) filtered lines changing how the background image is perceived I think is a close explanation. It’s not perfect, but kind of close.
I suppose the mixtures of the paint are chemistry to get the right layers but depending the level of the course I suppose an argument about using suspended particles and filter layers to change light could overlap with physics as well.
There are some versions that go on in one layer, though the specific processes for official currency are a little more exact.
Latest Answers