Karel Martens completed his studies at the Arnhem School of Art in 1961. Since then he has worked as a freelance graphic designer, specialising in typography. Among his clients have been the publishers Van Loghum Slaterus (Arnhem) in the 1960s, and the SUN (Nijmegen) 1975–81. In 1999 he designed the facade of the printing company Veenman in Ede, in collaboration with the writer K Schippers. In 2005 he designed glass facades for the Philharmonie in Haarlem. Martens has taught graphic design at the Arnhem School of Art, the Jan van Eyck Academie in Maastricht and the School of Art, Yale University. In 1998 he and Wigger Bierma founded the Werkplaats Typografie postgraduate course at the ArtEZ, Institute for the Arts, Arnhem.