Production and characterisation of lead, tin and antimony based yellow pigments

Abstract

This study deals with the preparation of yellow pigments (lead-tin yellow type I and II, lead antimoniate yellow and lead-tin-antimony yellow), which are affected by terminological confusion in the historical references. Through the centuries, yellows of different compositions, based on lead, tin and antimony, have been used either as agents that turn glasses, glazes and majolica opaque or as paint-pigments. Some types of yellow pigments were described in written sources. These sources are very hard to discover because production methods and formulas of artistic compounds were handed down to new generations in oral way. Sometimes, they were collected in secret books of pigments. In addition, artists and writers, during the utilization and production of lead-tin-antimony yellows, introduced some changes both in recipes and terminologies. All this produced great confusion in the nomenclature that changes the country tradition and, sometimes, for the writer’s inaccuracies.

By analyzing the various recipes concerning lead-tin-antimony yellows, it was possible to reconstruct the original production methods of these pigments. We produced lead-tin yellow type I (Pb2SnO4) and lead-tin yellow type II (PbSnO3 or PbSn1-x SixO3) following the indication of the recipes 272 and 273 of the fifteenth century Bolognese Manuscript, lead antimonate yellow, called Napoli yellow, according to the treatises written by Piccolpasso, Passeri and Mariano from Pesaro, and lead-tin-antimony yellow from the Darduin, Mariani da Pesaro and other recipes authors. The production of lead-tin-antimony based yellow pigments was obtained by pure chemicals oxides (PbO, Pb3O4, SnO2 and Sb2O3). In synthesizing the yellow pigments, the effects produced by changes in stoichiometric ratios, in melting temperatures and in the crucible typologies were tested. The obtained products were characterized by SEM-EDS, XRD and micro-Raman analyses. To evaluate colour changes due to different melting temperatures and stoichiometric ratios, the colour measurements were taken in CIE 1931 and CIE 1976 coordinates.

The results are analysed and discussed in terms of correlations among chemical compositions, melting conditions and colour hue. The study of these pigments, produced in laboratory with the ancient procedure, is also useful for investigations on similar materials used in the works of art. Indeed, it is very probable that the artists chose their painting materials by selecting not only the colour hue of the pigments but also the production method. Therefore, it is important to state a correlation between chemical compositions, ancient production methods, and the final colour hue of the produced yellow pigments.