Smalti Murano Glass Tessella’s Applied Outdoor in the Trencadís Catalan Modernism Mosaic: Recognition of Preliminary Alteration Patterns

This contribution presents previous results of a study carried out with the aim of achieving better results in the restoration processes by replacing the tiles of an exterior mosaic tiling of the Trencadís type of Catalan Modernism. In this case the trencadís tiles come from the cutting of pieces, called piastras, of opaque and mass-colored glass called Smalti Murano glass. These companies have extensive color catalogs that, although not exactly the same as they were a century ago, are close enough for these replacement tasks. Each color corresponds, however, to a different composition of glass and a slightly different manufacturing process. These differences favor that the differences of color always go accompanied also of differences of superficial aspect. However, not all color references currently available have the same surface quality since this product, during its manufacture, acquires primary defects typical of artisanal processes. So far the predominant criteria for the selection of the new references of piastras that must replace the product damaged by the extensive exposure to the weather as a coating are based primarily on color. However, durability requirements must also be part of the selection criteria for substitution references. The primary defects that a product already presents in its superficial quality are often indicators of either a more irregular quality or of circumstances that favor the early appearance of secondary defects throughout its useful life. The main objective of this study is to ensure, in restoration work by substitution, the selection of the best piastras from the point of view of surface quality, to apply on site the most similar tiles of tone and with greater durability. This study is part of a collaboration between the study group LiTA (Laboratori d'Innovació i Tecnologia de l'Arquitectura) (UPC) and a private non-profit organization.