The colours of Portuguese azulejos: a review

This paper summarises the available information to date on the pigments used on Portuguese azulejos between the late 16th century and the beginning of the 19th century. Most references cited focus on 17th-century tiles, followed by the 16th century, whereas there is very little information on the 18th and 19th centuries. Regardless of chronology, the Portuguese azulejo palette uses cobalt, copper, manganese, and iron oxides to obtain blue, green, purple, and dark brown, respectively. Yellow is obtained through the Naples yellow pigment, which could be mixed with cobalt for obtaining green, or with iron oxide for the orange colour. Blue and yellow are the most studied colours and the currently available knowledge allows us to relate changes in their chemical composition to specific time periods.