The inclusion of diffractive foil patches or stripes on substrates is common practice these days. Examples include the lower denomination EUR banknotes, which feature a continuous foil stripe. The stripe contains a diversity of security features, and can be authenticated by tilting the banknote – on a genuine banknote, the colour switches from green to gold. Karel Schell holds a physics degree from Delft University. Karel moved to security printer Joh. Enschedé (the Netherlands) in 1977 and joined the board in 1988. In April 1993, he established his own independent technological consultancy, enabling him to share his technological expertise and experience with a diversity of customers in Europe, Canada, the US, Africa and the Far East.