COPY AND PASTE? A CASE STUDY ON A PAIR OF JAMB FIGURES OF THE FÜRSTENPORTAL BAMBERG AND THEIR CASTS
Keywords: non-destructive testing methods, structured light scanning, 3D surface comparison, historic moulding process, plaster copies
Abstract. The focus of this paper is to determine whether it is possible to detect historical casting techniques on figural copies and distinguish differences due to these techniques from those caused by environmental influences after exposure to the weather. The figures from the Fürstenportal of Bamberg Cathedral of St. Peter and St. George, part of a UNESCO World Heritage site, have experienced much deterioration since the portal was erected in the early 13th century. For this reason, the jamb figures were moulded at the beginning of the 19th century and plaster copies made. These copies remained in safekeeping for over 90 years until they were used to make stone cast copies in the late 1990s. The copies replaced the outdoor originals, which were moved to a museum to protect them from further decay. It is therefore possible to observe different temporal states of the figures. Details of the moulding process could be identified with a workflow consisting of high-resolution 3D scanning, 3D surface comparisons and archival research. The plaster copies and the stone cast copies show different traces of the casting process. Both used flexible materials in the moulding process, which caused the copy to slightly deform from the originals. Furthermore, environmental influences could be separated from the moulding phenomena. Erosion from more than 90 years between the creation of the plaster copy and the translocation of the originals to the museum was observed, as well as erosion from the last 20 years on the stone cast copies.