Ionic‐Exchange Mechanism in the Formation of Medieval Luster Decorations

Abstract

Analysis of medieval luster ceramics seems to indicate that the formation of luster layers could involve an ion exchange between some alkali ions of the glaze (Na+ and K+), and copper and silver cations of the luster raw paint during firing. However, because of the weathering shown by the medieval luster decorations analyzed, conclusive proof is difficult to obtain. A realistic reproduction of the luster decorations has been fabricated in order to follow the process of formation of the luster layer. This has been studied by optical microscopy, transmission electron microscopy, electron probe microanalysis, extended X‐ray absorption fine structure, X‐ray absorption near‐edge structure, and the results give direct evidence that ion exchange and diffusion are the physical–chemical mechanisms responsible for the introduction of copper and silver into the glaze.

Metallic and nonmetallic shine in luster: An elastic ion backscattering study

“…6 The luster technique is very complex and includes ion exchange between Cu + and/or Ag + and alkaline ions from the glassy matrix ͑Na + and K + ͒, diffusion of the metal ions followed by nucleation, and growth in a reducing atmosphere to form metal copper and/or silver nanoparticles in the glass. [7][8][9] The materials and firing procedures used should be so carefully controlled that it is highly surprising that 9th AD potters managed to control the process so well, considering their limited scientific and technical knowledge.…”

Revisiting the beginnings of tin-opacified Islamic glazes

“…In the context of lustre decorated wares, it should be noted that the formation of lustre requires the presence of alkalis in reasonably high amounts, the process involving the diffusion of copper and silver ions from the lustre paint into the glaze where they substitute sodium and/or potassium ions which are removed from the glaze (Pradell et al, 2005;Molera et al, 2007). The subsequent increase in the lead oxide content of the lustre glazes (Mason and Tite, 1997) can then be explained in terms of a desire to reduce the extent of glaze crazing, resulting from the thermal expansion mismatch between high alkali glazes and earthenware bodies (Tite et al, 1998).…”

Nanoparticles in Ancient Materials: The Metallic Lustre Decorations of Medieval Ceramics

“…The role of ionic exchange was first identified in the lustre formation process (Smith et al 2003;Pradell, Molera et al 2005). From the analysis of medieval ceramics, some interesting trends and information were obtained concerning the driving force responsible for the diffusion of silver and copper ions into the glaze, consisting of an "ionic exchange" of Ag + and Cu + with Na + and K + .…”

“…Several descriptions of the glazing technique were proposed (Pérez-Arantegui, Molera et al 2001;Padeletti & Fermo 2003a;Colomban & Truong 2004;Pradell et al 2005;Roqué et al 2005;Pradell et al 2006;Roqué et al 2008;Colomban 2009) on the basis of experimental evidence and on information extracted from the transcription of ancient recipes (Abu al Qâsem 14 th century, Picolpasso 16 th century, Deck and Bertan 19 th century and Artigas 20 th century). Lustre decorations were obtained by applying a mixture of a paint, which contained copper and silver salts, water and more or less vinegar and lye, onto a glazed ceramic, which was subsequently annealed in a reducing atmosphere.…”