Glass-based pigments in painting: smalt blue and lead–tin yellow type II

Abstract

Glass-based pigments have an important role in the panorama of artistic production due to the fact that their manufacturing processes involve a combination of different skills and understanding, and they have a role in disciplines ranging from glass technology to metallurgy, from glazed ceramic to stone imitation and from vitreous mosaic tesserae to painting materials. The main goal of this manuscript is to present a critical review of the literature relating to blue smalt and “yellow glass” (lead–tin yellow type II) pigments: presenting their historical background, the analytical protocol, the processes of alteration and decay and finally tracing issues. Several case studies analyzed by the authors will be presented. Particular attention was devoted to the correlation between micro-textural features and decay processes affecting the studied pigments, though the widespread heterogeneity of the analyzed materials and the variability of the artistic techniques in which the pigments were used as well as the effect of the relevant (micro-)environmental conditions dictate a cautious approach. These studies are presented in the context of information about the chain of production, the selection of the raw materials and relevant provenance studies.

Revealing Juan de Oviedo y de la Bandera’s Artworks: The Case of the Polychrome of a Stone-Carved Sculpture from the Madre de Dios Convent Façade in Seville

“…The depletion of potassium ions created a deficiency in charge, which was compensated for with the ions around cobalt. This fact was responsible for some changes in the colour, as described in the literature [30,31]. passed since this polychrome was carried out, the potassium was possibly leached upon smalt degradation.…”

“…The depletion of potassium ions created a deficiency in charge, which was compensated for with the ions around cobalt. This fact was responsible for some changes in the colour, as described in the literature [30,31].…”

“…Historic documentary sources show that several grades were sold that varied in their colour intensity as a consequence of differences in both the particle size and the cobalt content [30]. The presence of arsenic in the sample could be associated with the presence of mineral sources such as erythrite (Co 3 (AsO 4 ) 2 •8H 2 O) or cobaltite ((Co,Fe)AsS) [16,17,31]. Smalt was also widely used in Sevillian ceramics [15].…”

Multi-Technique Diagnostic Investigation in View of the Restoration of “The Glory of St. Barbara” Painting by Mattia Preti

“…Finally, regarding the two samples with blue shades (S15, S21), a different chemical composition was detected. According to EDS data, sample S15 could be a smalt, a blue potash glass pigment where the blue color is due to the presence of Co [19][20][21][22]. Actually, the elemental chemical composition of sample S15 corresponds to that of the smalt pigment, with high Si, K and Co contents, followed by elements as impurities surely due to the raw materials used for the manufacturing process of the pigment, which does not allow a precise chemical formula to be proposed [19,22].…”

Analysis of two glass eye (Jatim) beads unearthed from the Northern Wei tomb complex in Dongxin, Datong

“…The orthorhombic Pb 2 SnO 4 transforms into cubic PbSnO 3 , which contributes to creating the yellow opaque color of the glass. If the temperature exceeds 950°C, PbSnO 3 decomposes [21].…”