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Kunsthaus Zürich

Antoine Bourdelle «Sappho» 1887/1925

Progress report November 2013

TECHNIQUE AND PRODUCTION OF THE SCULPTURE

Bourdelle’s bronze sculpture ‘Sappho’ is a sand casting made by the Parisian foundry of Alexis Rudier in 1925. It was cast in a number of parts that were assembled using a range of joining techniques. Endoscopic investigations of the interior of the central section revealed the presence of connecting bolts (see figure 1). In some areas, the arms overlap the parts of the sculpture to which they were attached, and the two were riveted together. Externally, these connections were concealed by brazing and chasing.

MEASURES CARRIED OUT

Once the quality of the surface had been analysed, careful wet cleaning was carried out to remove loose dirt, using soft plastic brushes, water and a mild, non-ionic surfactant. Wetting the surface with water creates an impression of depth that often conveys a clearer picture of the surface than when it is dry. This revealed that the brown deposits were remnants of a ground coat or paint layer, since brushstrokes can clearly be seen. The remains of shiny gold areas could also be made out on this layer.

Samples were taken and analysed by the Swiss Institute for Art Research (SIK-ISEA), Zurich. Cross-section polishes were made, which clearly revealed remnants of gilding (see figures 3 and 4). They also confirmed the assumption that the gilding had been applied over a surface that had already been exposed to weathering for decades. The analysis shows that it is gold leaf with an organic size which originally covered the entire surface of the sculpture. These remnants of coating are preserved as part of the sculpture’s history.

Following further preliminary tests and cleaning with soft brushes, the sculpture was then cleaned using hot steam and gentle pressure, which facilitated the removal of more firmly adhering dirt particles and airborne pollutants from the surface.
In certain places, such as undercuts, thicker and harder encrustations of sinter and dirt had formed. The only solution was to reduce these mechanically, working carefully with a scalpel to even out the differences of surface level. In all, though, only a few surfaces were treated in this way. The areas of green corrosion were not treated mechanically during the surface cleaning, as these are already below the original surface level, owing to weathering.

Fig. 1 Internal bolt connections with rusty bolts (image produced using the endoscope).
Fig. 1 Internal bolt connections with rusty bolts (image produced using the endoscope).
Fig. 2 Residues of the gilt coating, detail.
Fig. 2 Residues of the gilt coating, detail.
Fig. 3 Top view of a sample with remnants of
gilding. SIK-ISEA Zurich
Fig. 3 Top view of a sample with remnants of
gilding. SIK-ISEA Zurich
Fig. 4 Cross-section polish of the sample with gilding
SIK-ISEA Zurich
Fig. 4 Cross-section polish of the sample with gilding
SIK-ISEA Zurich

Antoine Bourdelle «Sappho» 1887/1925

Project description
Conservation and restauration work