Ancient Portuguese Ceramic Wall Tiles (“Azulejos”): Characterization of the Glaze and Ceramic Pigments

Abstract

Ancient ceramic wall tiles, called “azulejo”, firstly used on Portuguese churches, monasteries and palaces (15-18th century) have progressively been used in particular houses till the last century. These tiles and its use in huge decorative panels can be considered as a precious but fragile cultural heritage from Brazil to India, in several countries influenced by Portuguese culture. Morphologically, these tiles are composed by a porous clay-based ceramic body, the terracotta, covered by a protective glassy phase, the glaze. As artistic paintings, these murals incorporated various kinds of pigments in the glaze layer to create a pictorial impact on the walls of rich palaces or churches, real and durable monumental works-of-art. In the 21st century, degradation marks are visible on these ceramic tiles because of their use under corrosive conditions (moisture, atmospheric cycles…) along centuries. In order to promote their conservation and enhance their restoration, the physical-chemical characterization of the azulejos is performed in the present work, using mainly non-destructive processes like micro-Raman spectroscopy or X-Ray diffraction. In particular, Raman spectroscopy allows the detection of some nano/microcrystals present in the amorphous glaze due to pigments or opacifying agents or related to the elaboration process of the azulejo. Based on the observation of various selected fragments, one states that very few pigments have been used as colouring agents in this ceramic art during 17-18th centuries. Thus, the relationship between the different colours, the introduced pigments and the structural aspects of the glass will be focused. Some features related with the ancient ceramic technology will also be discussed.

Raman spectroscopy applied to early (ca. 1746–1754) English steatitic porcelains: a tentative study of compositions

“…Yellow: (Pb-Sb-Sn pyrochlore) [54] 340, 450, 507, 615 Ware illustrated in Fig. 1(a) Blue-green (turquoise) [55] : (Figs 6 and 7) Bow Red [50] : Ware illustrated in Fig.…”

“…A colour with a similar Raman spectrum was reported by Pereira to have been used to decorate 'azulejo' ceramic wall tiles. [54] These tiles were first used on Portuguese churches, monasteries and palaces in the 15th century. The peak at 778 cm −1 could be assigned to microcrystals of cassiterite and the peak at 618 cm −1 to Fe, which would suggest that an iron oxide pigment has not been integrated into the pyrochlore structure (as was found by Pereira).…”

On-site Raman analysis of 17th and 18th century Limoges enamels: Implications on the European cobalt sources and the technological relationship between Limoges and Chinese enamels

“…[30][31][32][33][34][35]. The compositional analyses of Famille Rose, Famille Verte and cloisonné wares as well as cloisonné enamels on metal have been reported by a few authors [21,24,25,[35][36][37][38], but as noted by Kingery and Vandiver in 1986, "the descriptions of the enamel technology are completely speculative" [24] due to the very small number of artefacts studied.…”

The historical glazed tiles from Nossa Senhora da Soledade Cemetery, Northern Brazil: microstructural, physical and mineralogical characterization

“…Cobalt is responsible for the blue color of the analyzed patterns [5,6,9,14]. Manganese identified in orange-brown and black shades of sample AZ.N33 is associated with antimony and iron to achieve the desired color [5,8,9,11].…”

“…The base of the vitreous matrix is composed primarily of PbO and SiO 2 , with additions of other elements such as CaO and K 2 O used as fluxes, possibly in the form of a calcium carbonate and a K-feldspar [5,7]. Tin predominates in the white glaze, used extensively in the Portuguese manufacture of majolica stamp and relief tiles from the seventeenth to the nineteenth centuries, because it guarantees the separation of chromophore oxides and the opacity of the glaze [6,[8][9][10][11][12]. For the decoration, the colors were obtained from metallic oxides, such as copper, cobalt, iron, manganese, or synthesized pigments, which were used alone or mixed with other pigments [5,8,9,13].…”