The archival material, which is at the NAI, consists of photographs of his works, documentation, examination papers from his training days and personalia. An important component is the book "Ars Sacra," edited by Van Hardeveld in collaboration with the St. Bernulphus Guild in 1929. This book provides an overview of sacred art from the early 20th century. Under code CAND (Collection Archives of Negatives and Slides) are the glass slides used for the purpose of the illustrations for this publication. The archive consists of a large flat box and two small cardboard boxes. A brief description follows.