Using non-destructive methods of analysis such as X-ray fluorescence or Raman and VIS spectroscopy, the scientists – working under Johan Oosterman (Radboud University), Everardus Overgaauw (Manuscript Department of the Staatsbibliothek zu Berlin) and Ina Reiche (Rathgen Forschungslabor) – have also been able to gain important insights into technical aspects of the book’s artwork. Whereas the faces and details like the hair are elaborated with great care in some of the illustrations, they are rendered rather as a general impression in others. They were distinguishable primarily by the size of the illustrations and their level of precision. Among the most interesting findings was that at least five different artists had worked on the book. Parallel to the physical aspect, the manuscript was analyzed from the art historian’s perspective. The interdisciplinary team of art historians, philologists, restorers, and scientists analyzed the damage and developed a strategy to preserve the valuable book over the long term. Stabilizing the paint surfaces on almost five hundred pages is very time-consuming work, and the restoration process is still under way. Some pages of the prayer book that have already been restored have been presented to the public in the museum’s exhibition I, Mary of Guelders (the name under which she is better known in the Netherlands). Additional participants in the project, which is sponsored by the Ernst von Siemens Art Foundation, include the Helmholtz Center for Materials and Energy, the Max Planck Institute of Colloids and Interfaces, and the Valkhof Museum in Nijmegen. 42) from a Materials Science and Codicological Perspective' in order to unravel the mysteries of the manuscript. In 2015, scholars and scientists at the Staatsbibliothek zu Berlin, the Rathgen Forschungslabor (Rathgen Research Laboratory) of the Staatliche Museen zu Berlin (National Museums in Berlin) and Radboud University of Nijmegen launched an interdisciplinary research project titled 'The Prayer Book of Marie d'Harcourt (Ms. The damage to the vellum can very likely be attributed to mechanical forces caused by different bindings applied to the manuscript, in combination with fluctuations in climatic conditions. To a great extent, the damage to the paint surfaces is due both to the age of the materials used and the climatic influences of storage environments that have sometimes varied dramatically. An inventory of the deterioration includes cracks in the vellum, worn and flaking paint, rubbed-off gold leaf, chalking paint surfaces and the fine pattern of dense cracking known as 'craquelure,' all of which have made the prayer book so fragile that no routine handling of it has been possible since the early 1990s. Unfortunately, however, this proud 600-year-old work is in a pitiful condition. The prayer book of Marie d'Harcourt has long been considered a showpiece of the Dutch manuscript illumination of the Middle Ages. The book contains personalized prayers and verses, some of which were composed exclusively for the duchess in the local dialect of East Middle Dutch. The finished work is a magnificent volume, with 92 miniatures of outstanding artistic quality interspersed with the text, along with numerous historiated initials and decorated margins.

He had the assistance of at least five artists, who created a multitude of colorful miniatures and drolleries to adorn the 482 vellum pages of the book. The monk and scribe Helmich de Lewe worked on the book at the Augustinian monastery of Marienborn, near Arnhem, and completed the project in 1415. So it is no surprise that the book of hours of Marie d'Harcourt, Duchess of Guelders, is one of the most beautiful medieval manuscripts held in the collection of the Staatsbibliothek zu Berlin (Berlin State Library). When a duchess commissioned something in the fifteenth century, those around her moved heaven and earth to guarantee the most exquisite product. Since 2015, conservators have been comprehensively examining and restoring the richly decorated medieval manuscript as part of a major research project involving the Staatsbibliothek zu Berlin, the Rathgen Forschungslabor and Radboud University in the Netherlands.

The book of hours of Marie d'Harcourt is one of the most beautiful manuscripts held by the Staatsbibliothek zu Berlin.

Illuminated manuscript project