ZURICH.- The bronze sculpture ‘Sappho’ by the French artist Antoine Bourdelle (1861-1929) is currently undergoing extensive restoration at the Kunsthaus Zürich. A collection presentation is planned for 2014.

Along with Auguste Rodin and Aristide Maillol, Antoine Bourdelle formed the triumvirate of early modern French sculptors. Originally from south-western France, Bourdelle found worldwide recognition during his lifetime. His output ranged from intimate, small-scale works to large public commissions in a variety of formats. His main focus was on depicting the animated and powerful human figure down to the smallest details, often in mythological contexts. The three important bronzes held by the Kunsthaus Zürich also fall into this category: ‘Apollon (Masque)’ from 1900, a representation of the face of Apollo, the Greek god of music and poetry; ‘Beethoven’ from 1902, a bust of the famous composer – and ‘Sappho’ from 1887/1925.

SAPPHO’S MAIN SUBJECT IS LOVE
Bourdelle’s ‘Sappho’ is a monumental representation of the greatest female poet of antiquity (late 7th to early 6th century BC). She is shown with a large lyre, crouching on a small rocky elevation. The whole figure is filled with tension, from the raised big toe of the right foot, to the right hand, which is held aloft; and that tension also manifests itself in the folds of her dress. Sappho has her head bowed. Her right hand, raised above her head, mirrors the form of the musical instrument. Perhaps the poet is deep in thought, counting the metre of a poem. Sappho’s main subject is love – and her admiration for the goddess of love Aphrodite.

A BADLY WEATHERED BRONZE
Bourdelle worked on his Sappho composition several times. He completed his first version, which was just 28 cm in height, in 1887. In 1924 he finished a 70-cm bronze sculpture, followed a year later by the monumental bronze work, of which seven castings exist. The larger than life-size example from 1925 in the Kunsthaus has the typical appearance of a bronze that has been exhibited outdoors for many years, with conspicuously green and black areas. They are the products of copper corrosion, predominantly alkaline copper sulphates and accretions of dirt. The green corrosion products – in the form of coarse and fine crystals and in some cases a powder – have little adhesion to the underlying material. The black particles, by contrast, are smooth and firmly impacted in the surface. They occur in patches dotted over the underlying green. On close examination, it is evident that the surface has a number of levels. The light green corrosion products, sometimes shading into blue, are somewhat deeper – a sign that the surface has already lost layer thickness. In the urban environment, moisture combines with the atmosphere to form acidic solutions which prevent the build-up of a compact, passivating layer. It is therefore no surprise that deep streaks have formed on the surface over the decades.

MEASURES CARRIED OUT
Once the quality of the surface had been analysed, careful wet cleaning was carried out to remove loose dirt, using plastic brushes and water with the addition of a mild, non-ionic surfactant. Wetting the surface with water creates an impression of depth that 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, resulting from earlier decoration. Unresolved questions concerning this surface phenomenon were answered using samples that were analysed by the Swiss Institute for Art Research. Following preliminary tests and cleaning with soft brushes, the sculpture was then cleaned using hot steam and gentle pressure, which facilitated the removal of 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.

HELPING THE SCULPTURE TO PROTECT ITSELF
Accordingly, and also for aesthetic reasons, the surface was subjected to conservation with wax. This provides lasting protection against weathering and vandalism, but also enables a stable, self-healing and protective bronze surface to ‘regenerate.’ The wax used was the microcrystalline Cosmoloid H 80, which has a high melting range. It is dissolved in white spirit and applied, allowing it to melt into the surface while hot. This offers long-term protection but requires regular maintenance.

FINAL STEPS BEFORE THE 2014 EXHIBITION
Following the conservation overseen by Hanspeter Marty, Patrick Decker will carry out partial retouching limited to isolated, particularly unsightly areas to restore the surface to something closer to its original appearance and enhance the visual readability of the artistic form by emphasizing certain characteristics. As with every step, this will be carried out in close, interdisciplinary coordination with collection curator Philippe Büttner. The restoration is expected to be complete by the end of 2013. From 21 March to 22 June 2014 the Kunsthaus will then be staging an exhibition of the Bourdelle sculptures from its collection. This will be accompanied by detailed information about the artist, his work and the latest developments in the restoration. A report on some of the measures taken can already be seen at www.kunsthaus.ch under The Collection > Conservation.