Community Research and Development Information Service - CORDIS

New conservation methods for outdoor bronze sculptures

Works of art standing outdoors are endangered by environmental impact, which accelerates their natural degredation. Unsheltered metal objects, like bronze sculptures, originally polished, waxed or artificially painted, are susceptible to corrosion due to the attack of rain or condensed water and pollutants. The surface changes in colour, in chemical composition and in the amorphous character of the patina. Preserving the artistic intention of these art objects has induced conservators to reflect about methods of maintenance.

Currently available coating systems have proved to have only a restricted long-term stability (about 5 to 10 years). This is not ideal from a conservation point of view, since failed treatments have to be repeated within a short time, thus raising the costs of maintenance.

A promising attempt has been made to introduce a new class of material for the protection of outdoor bronze sculptures: organic-inorganic copolymers (organically modified ceramics), incorporating properties of organic and inorganic materials. A multidisciplinary team of experts in surface coating technology, metal corrosion and bronze conservation from different countries worked together for two years, developing the new material and testing for the given purpose.

The efficacy of various Ormocer systems as protective coatings was evaluated on a large number of different bronze substrates simulating uncorroded as well as patinated surfaces. The laboratory phase included extended test series of the coated samples to optimize adhesion properties and long-term stability. The protective treatments were evaluated according to the results of a broad variety of analytical methods after exposing the samples to accelerated weathering. At the end of the project, promising Ormocer coatings were applied to two bronze busts and one original statue. Their long-term exposure outdoors will demonstrate the performance of the proposed treatment under natural weathering conditions. The results obtained from these pilot studies will direct future research on Ormocers as new coating systems for massive outdoor sculptures.

Reported by

Institut für Silicatforschung
Bronnbach 28
97877 Wertheim
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