Counting Vermeer


Foreword : Counting on the RKD — Chris Stolwijk and Sytske Weidema

A sunny spring afternoon more than ten years ago. On the initiative of C. Richard Johnson, Jr., the Geoffrey S. M. Hedrick Senior Professor of Engineering at Cornell University (Ithaca, NY), the Research Department of the Van Gogh Museum starts a series of workshops on the analysis of brushstrokes. A group of art historians, conservators and computer scientists explores the possibilities of the application of computational techniques and methodologies to address current issues in art history. These workshops and the many discussions between the colleagues participating led to the foundation of the Thread Count Automation Project (TCAP) in late 2007. Eventually, TCAP focused on the works of Vincent van Gogh, but from the very start also opened its activities towards Old Master painting, including projects on and works by Rembrandt and Vermeer. Since, the automated thread counting from X-radiographs of paintings on canvas has proven to be a highly innovative development. It provides not only masses of (forensic) data, but especially has changed the time-consuming, traditional (and manual) methodology of thread counting used by conservators for many decades. TCAP has opened new research fields and research questions such as artists’ practices, the authenticity of paintings and the production of canvas and canvas rolls of which little was known before 2007.

From the very start of TCAP the RKD – Netherlands Institute for Art History was involved in the project, mainly through the Rembrandt Database and colleagues working on the RKD’s collection of technical documentation, created during technical studies and the restoration of artworks. Another result of the involvement of the RKD is this publication, Counting Vermeer, which Arthur Wheelock in his introductory essay describes as a result of ‘a new type of scientific examination of paintings: computer-generated “weave maps”.’ These maps are generated on the basis of the above-mentioned innovative development of automated thread counting from X-radiographs of paintings on canvas. They provide a wealth of new information ‘about threads and weave patterns with such precision that scholars can compare the character of the canvas supports of different paintings.’

Technical documentation
The RKD is well known for its collection of over six million photographs, reproductions and slides of mainly Dutch and Flemish artworks in an international context. Up to this date researchers from all over the world come to the RKD to study these visual documents. The RKD also holds the largest art historical library in the Netherlands, including special items such as rare auction catalogues. Some 700 archives, concerning artists, art historians, art dealers, art collectors and art restorers, are open for research.

Less known is the RKD’s important collection of technical documentation. Technical research is increasingly becoming a standard procedure during (art historical) research and plays a part in it. Technical examination is performed in the course of exhibitions, for collection catalogues, for conservation purposes, or, also increasingly, for research projects, such as the Science4Arts program. Although normally results are being published, a large part of the technical documents quite often remains hidden in archives, hard drives or personal files. Up to this date institutions and individuals give less priority to properly structure and store the documentation, or they simply are not able to or do not know what to do with this documentation. This is an unfortunate situation, since many documents are essential for further research, renewed examination, or restoration projects.

Since the 1990s the RKD actively collects technical documentation, either in digital or analogue form. The RKD also carries out infrared reflectography examination (IRR), of which the results are added to the technical documentation collection. The present documentation consists of the results of a variety of research techniques, including infrared reflectography, UV, X-radiography, paint sample analysis, etcetera and documentation pertaining to the treatment of objects. The aim of collecting technical material is to enable researchers to have better access to these research documents, preferably in the context of other types of related material at the RKD. This documentation is systematically entered into the existing RKD’s databases, combining it with art historical information. As such, the technical research documentation is embedded in its art historical context. The technical research data is available online via RKD Explore: Also, the documents can be studied and requested at the RKD. Further embedding technical documentation in its art historical context is part of the RKD’s initiative to develop a state-of-the-art digital infrastructure, RKD Research.

Documentation archives
Among the technical documentation archives of the RKD is the material of Professor J.R.J. van Asperen de Boer, Professor M. Faries and Professor M. W. Ainsworth, containing the IRR negatives and manual assemblies of thousands of paintings and related text and image documentation. They also include several conservators’ archives, such as those from C.F.L. de Wild, Dr A.M. de Wild, P.F.J.M. Hermesdorf and the restoration foundation Stichting Kollektief Restauratieatelier Amsterdam (SKRA), containing a variety of technical research documentation and correspondence and IRR, UV and X-ray documents of the exhibition and publication Mondrian: The Transatlantic Paintings (2001), organized by Harvard University Art Museums (HUAM).

The RKD pays special attention to dendrochronology research on art, via the dendrochronology platform and database Dendro4Art. The RKD collaborates with dendrochronologists worldwide, such as Professor Peter Klein who shares thousands of dendrochronology reports and other types of data with the academic public. His reports and raw data were digitized and entered into the RKD’s databases along with art historical information on the paintings.
It is in particular worth mentioning the archive of the Rembrandt Research Project (RRP) now in the collection of the RKD. Apart from a large amount of notes, correspondence, transcripts of auction catalogues, (copies of) photographs, infrareds, paint sample documentation and other research data on more than 600 Rembrandt paintings, the collection contains a fairly complete set of (prints of) X-ray films. In the frame of the Rembrandt Database project these films are being digitized and can be used for study purposes and other research projects. Already hundreds of X-ray films at the RKD and other institutions have been digitized, assembled, and published via the Rembrandt Database website ( This website enables researchers and other professionals to share their research material and information via the RKD with the academic public.

Though currently the database focuses on Rembrandt paintings, the RKD will provide the database as format for other artists or projects from 2018 onwards. The resource is embedded in the RKD database infrastructure and as such contains extensive art historical object data and presents technical documentation and information.


1 Rick Johnson in an early stage has been able to use these digitized assembled X-rays for the development of his thread count algorithm and in particular for his angle map project.

Cookies disclaimer

Our site saves small pieces of text information (cookies) on your device in order to deliver better content and for statistical purposes. You can disable the usage of cookies by changing the settings of your browser. By browsing our website without changing the browser settings you grant us permission to store that information on your device.
I agree