Abstract

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.

Abstract

Gold leaf Murano glass is a unique product that over the centuries, especially during Byzantine period, has been used as facing forming big flat or curved mosaics that result in an architecture full of light and symbolism. This product is presented in a format of squared piastras with the same approximate dimensions that the gold leaves ones have (8x8 cm). Piastras are cut in smaller squares (1-1,5cm) in order to obtain the tiles that form mosaic’s cladding. This cladding technique was incorporated during Catalan Modernism. Through this technique, beautiful pieces of tesseras of gold leaf Murano glass combined with others of opaline glass. In order to overcome the artistic challenges from this architectural movement, new mosaics were placed outdoors in order to shine by the incident sun beams and the square tiles were replaced by irregular tiles that form polygonal meshes capable of coating double curvature surfaces with great elegance. This location and prolonged exposure to the weather cause, over time, a deteriorated appearance, despite being composed of great resistant materials such as gold and glass. Studies oriented to know the phenomenology of this deterioration are being carried out and its impact on the expected durability of this coating. Being a handmade product and completely manual execution, the first studies have aimed to identify the primary anomalies that are originally generated in the different layers of this product at the time of manufacture, transport and handling. Knowing these primary anomalies must allow to prevent their occurrence and reduce their incidence in the manifestation of so-called secondary anomalies. All this in order to prolong the useful life of this appreciated architectural cladding.