Paul Zwartkruis collected paintings of modern and contemporary artists. Later on, he started to collect lithographs, etchings and woodcuts and bought a book about the School of Paris (École de Paris), in which an international group of artists such as Picasso, Matisse, Braque, Laurencin, Delaunay, Chagall and others were described.
These artists from the first half of the 20th century had his special interest. Back in the nineties, Paul stumbled upon a book about Matisse, the book disclosed 5 colorful (visual art) stencils, that turned out to be pochoirs. Pochoirs are handmade reproductions of artwork, produced in Parisian ateliers by female staff members during the period 1920-1960. A very costly, labor-intensive technique.