A tour of façade azulejos decay in Lisbon

Abstract

In this communication we walk through the streets of Lisbon to review the degradation of the 19th century tiled façades and assess its causes. The communication opens with a synthesis of overall principles derived from the observations and proceeds to discuss the causes of the detachments from the façades, which are a degradation of the tile coverings and not of the azulejos themselves. The adherence of the glaze to the ceramic body is then shown to be a capital factor underlying azulejo decay. Within this heading crazing, spalling and blistering are successively discussed. In the conclusive notes, the glaze adherence is presented as a time dependent propriety whose chemical decay is a subject open for research.