 Additional suppliers include German company Gleitsmann Security Inks, Sun Chemical (through their Brand Protection Division based in Manchester, UK), the Brazilian company Sellerink, located in São Paulo, Brazil and the Swiss company Printcolor Screen AG, located in Berikon, Switzerland.Color-shifting inks reflect various wavelengths in white light differently, depending on the angle of incidence to the surface.An unaided eye will observe this effect as a change of color while the viewing angle is changed.