Monitoring of historical stucco by means of a strip light projector at the Château de Germolles

Finished
Tobias Reich and Christian Degrigny preparing the stucco for the capture i3mainz, CC BY SA 4.0

The aim of the cooperation project between the i3mainz and the Sarl Germolles, represented by Prof. Christian Degrigny, is to monitor the changes and deformations and deformations of the stucco applications of the dressing room of Margarethe of Bavaria over several measurement campaigns to detect, analyze and document

Motivation

Located in the heart of Burgundy, near Beaune and Chalon-sur-Saône, is Germolles Castle, the best preserved residence of the Dukes of Burgundy. Built in the second half of the 14th century, this complex reflects an important page in the regional history. The castle is also one of the few preserved examples of the design of the living quarters in France of the 14th and the first half of the 15th century, as most of the princely palaces from this period have disappeared. (Wikipedia)

A very well preserved part of the palace is the dressing room of Margarethe of Bavaria. Particularly noteworthy are the very beautifully decorated walls with murals and stucco elements dating from the time.

In historical buildings, such as the above-mentioned chateau, materials of different types and quality were often used, which, due to the unique state of preservation, are difficult to analyze without damaging the respective elements. However, since movements and deformations can occur, caused by the architectural construction, the material used or by external influences (temperature, humidity), it is desirable to localize and analyze these deformations. In this way, it is possible to deduce the causes of cracking or similar phenomena. In the Chateau Germolles, precisely such phenomena (cracking, spalling) occur in the dressing room of Margarethe of Bavaria described at the outset. These are mainly located in the stucco area of the ceiling. The aim of the cooperation project between i3mainz and Sarl Germolles, represented by Prof. Christian Degrigny, is to detect, analyze and document the changes and deformations of the stucco applications over several measurement campaigns. Due to the expected deformations, which will primarily be in the sub-millimeter range, a measuring system must be selected that is capable of scanning the application surface in sufficient detail and also provides the accuracy to detect geometric changes of a few tenths of a millimeter. Based on the requirements, the three-dimensional recording of the stucco surface is carried out by means of active stereophotogrammetry. For this purpose, a close-range scanner from GOM with a spatial resolution of 0.2 mm and a depth accuracy of approx. 0.05 mm (depending on material and surface condition) is used.  In order to be able to make a statement about the possible changes in the stucco due to e.g. temperature-related influences, a total of four measurement campaigns will be carried out at different times of the year.

Activities

In a first measurement campaign in June 2018, the basic survey for the following the following measurement campaigns was carried out. In order to guarantee stable and comparable and comparable measurements over the total of four measurement campaigns, permanent permanently attached reference points are necessary. These were established before the actual in cooperation with Christian Degrigny, the local restorer, before the actual measurement process. restorer, in the entire stucco area before the actual measurement process. Since these points not only to support the measurements by means of the strip light projection scanner scanner, but are also used to link the individual measurement campaigns. it is necessary to determine the coordinates of the reference points photogrammetrically prior to the to determine the coordinates of the reference points photogrammetrically before the scanning process. From the combination of photogrammetry and active stereophotogrammetry, the entire stucco area can be recorded. stucco area can be recorded.

The second measurement campaign was timed to coincide with the start of the heating season at Château de Germolles. Here, it was checked whether these temperature-related climatic changes would affect the stucco.

Results

The first measurement campaign provides the geometrically highly accurate basis for monitoring, in the form of a digital 3D model of the complete stucco applications. After the technical measurement of the stucco in the second the second measurement campaign, an initial comparison can be made with the data from the previous measurement campaign is possible.