A technical study of the plaster decoration in the Villa of the Argotti Botanic Gardens, Floriana, Malta

Abstract

This dissertation is focused on a plaster relief found in the Argotti Villa which is located in the Argotti Botanic Gardens in Floriana, Malta. This plaster relief has not been previously studied. The aims of this dissertation focus on studying the relief’s technology, original technique and its overall condition. The plaster relief in the Villa can be described as a relief built layer by layer in situ, on the stone primary support. There is more than one support system anchoring the relief to the wall. A total of three main plaster layers were observed to make up the relief. Examination on-site was complemented with analyses of samples taken from the relief. The samples were investigated through a stereomicroscope, Polarized Light Microscope (PLM) and Scanning Electron Microscope (SEM) combined with Energy Dispersive X-ray Analysis (EDX). The plasters are composed of carbonated lime as the binder. Aggregates are of different nature: carbonatic aggregates are mainly present (possibly from local limestone, showing fossils), gypsum (in its mineral form) aggregates and to a much lower extent silicate-aluminate aggregates. The technology and some of the original materials of the relief showed similarities to the plasters of the mosaiced relief of a Nymphaeum, which is also located in the Argotti Botanic Gardens like the Villa. Physical evidence of other painted plasters in the room suggests the presence in the past of a larger decorative scheme: these include remaining of a painted plaster above the relief (which partially goes behind it) and a painted reddish plaster in the low register of the room. The condition survey and analysis of the plaster relief at the Argotti Villa showed the presence of salts, which are a major cause of deterioration. Mainly chlorides and sulphates were identified on the plastered relief, and on the surrounding plasters and stone in the room. Sodium chloride is widely present, and it was detected through SEM-EDX analysis. Environmental monitoring data recorded at the Argotti Villa were analysed to determine if soluble salts are active. The date when the plaster relief was made is still unknown and further research is needed to gather more information on this and on the decorative scheme. However, a terminus post quem (post-1715) and a terminus ante quem (c. 1800-1827) are given for the construction of the Argotti Villa. Conservation suggestions were provided to safeguard the plaster relief.