Filling and retouching techniques in outdoor tiles with saline efflorescence problems. A case study

Abstract

This article will be focusing on a retouching conservation and restoration treatment, of two figurative ceramic tiles panels belonging to the Baroque artistic period. The ceramic tiles of blue and white colors dating from the final of the 18th century are inserted in a relevant historical period for the Portuguese tiles art entitled Grande produção Joanina. The purpose of the intervention was the return the readability of the scenes in the panels, without hiding major signs of degradation. This conservation treatment was made within a rehabilitation project of the building that holds them, which had its own intervention criteria and in which the conservation criteria had to fit. One of the issues during this case study, was to find a commitment between the conservation ethical approaches, considering the panels will continue to be exposed outdoors and there are soluble salts present on the wall where they are settled. The intervention criteria chosen was made, using diverse solutions within materials and techniques such as the application of new ceramic elements, filling gaps with lime mortars and al fresco retouching. A capillarity and permeability based method was used to fill the glazed gaps. Retouching methods were tested including neutral tone or continuing the shapes and tones. In the end al fresco retouching method was chosen and the preparation of the new ceramic elements supported by a study of graphic and photographic documentation, completing the big gaps in the panels. The results of the chosen al fresco technique show a satisfactory level of mimicry, enough to return the readability of the panel. This technique revealed to be suitable for the retouching of ceramic substrates affected by soluble salts. The reading of the scene panels became passively also, by completion the missing parts, with the introduction of new elements what, was achieved with success too.