Conservation and Restoration of the Don José I Monument in Lisbon, Portugal. Part I: Stone Components

The equestrian statue of D. José I, in Lisbon, Portugal, stands on an elegant and decorated plinth fashioned in a very dense limestone. The sculptor, Joaquim Machado de Castro, designed the pedestal with colossal stone pieces and selected one of the best Portuguese stones for this purpose, the Lioz limestone. The same stone was also used for the flanking sculpture groups and the base This stone is a very pure reef limestone, rich in fossils and a low porosity <1 %. It is extremely compact and highly resistant, even in the harsh environment of a busy metropolis and within the impact of marine winds. The generalized deterioration is surface erosion caused by direct runoff water, with some incipient black crusts and soiling incrustations occurring in sheltered places. In some areas copper stains originating from the metal statue were also found. An extensive network of cracks was found, mostly at or near the top of the plinth, which could be ascribed to the presence of iron rods and clamps left inside the structure to hold the stone pieces together. During the intervention, these cracks were sealed with a multi-barrier system, given the impossibility to access the interior to remove or directly passivate the iron inclusions. Inoperative joints were cleaned out and repointed. Black deposits could be eliminated by nebulized water and soft brushing while the copper stains required the application of poultices with ammonium carbonate, in some cases requiring the addition of a complexing agent.