The Colour of Soil

DNB Betalingsverkeer
Date 9 November 2010

In this paper the colour of soil on banknotes is revealed. It is demonstrated that soiling changes the spectral reflectance of the banknote surface mainly in the blue part of the spectrum, i.e. soil on banknotes has a distinct yellowish/brownish tint. For euro banknotes the best option to detect soil is a reflection measurement in the blue part of the visual spectrum, more precise around 450 nm. This can be achieved using either using a blue illumination for the soil sensor or using a form of white light and using a blue filter in front of the light capturing device.