Façade of Santa Maria del Giglio
This church was built in the second half of the seventeenth century by Giuseppe Benoni; the façade is the work of Giuseppe Sardi.Antonio Barbaro left detailed instructions in his will for the design, building and financing of this church, which was intended to glorify the generosity of the donor and his family. The themes represented on the richly decorated façade are profane and, indeed, war-like, with little relation to the religious function of a church.
The upper half of the façade is decorated with representations of civic and military virtues. Statues of Antonio’s four brothers stand in niches on either side of the entrance. Below, the plinths of a solid stylobate are decorated with relief plans of cities and naval battles illustrating the career of Antonio Barbaro, whose statue stands right in the centre of the façade.
The façade is of Istrian stone, but the statues of Barbaro and his four brothers, the niche, the urn and the coats of arms are sculpted in Carrara marble.
Description of deterioration
A thick black deposit made it impossible to appreciate the decoration and sculpted stonework at ground level, while the second level and the semi-circular pediment were disfigured by the run-off of rainwater.
Although the marble statues were well preserved (having been treated at the time that the façade was built with a protective linseed oil-based preparation), the marble sculptures on the second storey were in a serious state of disintegration.
Fragments of stone were falling off and the walls were fissured as a result of nails expanding as they rusted.
1. Preliminary studies
Thorough studies were carried out, and the instances of decay in the façade listed before laboratory investigations began.
A survey by the Interdepartmental Cartography and Photogrammetry Centre of the International University of Architecture in Venice provided a detailed architectural description and an overall view of the work to be planned.
The materials were analysed. Specimens were taken for mineralogical and petrographic analyses which corroborated the information in the archives on the use of Istrian stone and Carrara marble. Metallic elements were also analysed, revealing a predominantly copper-based alloy. All the metals showed surface damage due to copper sulphation, which itself was caused by atmospheric pollution.
Hidden nails had therefore to be located with the greatest possible precision so as to assess their state of conservation and structural function.
Magnetic investigations, hampered by the presence of metallic tubes in the scaffolding, revealed 40 hidden nails set out fairly regularly.
2. The remedies applied
The various items to be restored were studied separately: marble statues, stonework, copper alloys and iron components were all studied in special programmes.
Cleaning of the façade was essential in order to slow down the decay of stonework by eliminating the infiltrated soluble salts and preparing the façade to receive new consolidation products.
- cleaning the stone
Bird droppings were rubbed off or, where necessary, removed with a scalpel. Once the decayed parts of the stone had been consolidated, the surface was steamblasted with distilled water, care being taken to protect marble elements and to fill in fissures temporarily so as to prevent the water penetrating the stone.
- cleaning the marble
Compresses saturated with a 10 per cent concentrate of ammonia were applied, with varying supports and for varying periods of time depending on the characteristics of the elements to be cleaned. The four statues of the brothers were treated in their entirety, while in the case of less visible parts only the damaged surfaces were cleaned. Where compresses were not enough, the cleaning process was completed by micro-sandblasting.
As the operation proceeded, more was learned about the state of conservation, and pre-consolidation work became more effective in consequence.
Cleaning also revealed some aspects of the building not noted in the documents, such as traces left by the tools used or a gradual slackening of standards in finishing details as time ran out.
After cleaning, protective consolidating products were applied which had been tested on specimen pieces, and an anti-pigeon system was installed on the ledges which seems to be most exposed to droppings. Only areas at risk were protected, so as to leave sightseers as clear a view as possible of façade.
The system adopted consists of suitably placed electrical wiring, PVC spikes to prevent pigeons settling on ledges, and galvanized copper wires.
Work on the façade of the church will continue until 2001, and will include an assessment of the quality of the interventions carried out.
Special attention will be paid to the period of duration of the damp-proofing, any signs of colour changes, the effectiveness of the anti-pigeon system, the evolution of fissures and the state of stonework left untouched by the restoration.Naturally, any necessary repairs will then be carried out.
Lead Organization / Sector / Office: The "Pro Venezia" Foundation Switzerland