Electroanalytical Study of the Composition of the Raw Pigment Mixtures that Yield the Metallic Lustre on Ceramics. A Link Between Composition and Final Result

Abstract

Voltammetry of immobilized microparticles was used to study the electrochemistry of the raw pigments that produce the metallic lustre on ceramics after a successful firing. To study this influence of the mixture components on the reduction properties to achieve the metallic lustre, 14 mixtures of illitic clay, Fe 2 O 3 , HgS, CuO and AgNO 3 were prepared and studied in different media. Iron oxide improves the yield of the reduction of the metals and cinnabar helps a closer reduction of silver to copper reduction and prevents the AgÀCu alloying because of the formation of silver -mercury adducts. The presence of one of the metals influences the peak position of the other metal. The use of vinegar as diluting agent is not casual, because in this media the reduction of silver takes place at a potential closer to the copper. This electroanalytical technique allowed to distinguish between powders of different composition and offered some information about the role of the components in the reduction of copper and silver and the selection of vinegar to prepare the raw pigment suspensions.

Characterization of prehispanic cosmetics found in a burial of the ancient city of Teotihuacan (Mexico)

“…7) because the square wave excitation technique provides simultaneously reduction and oxidation signals. In agreement with literature (Lange et al, 1993;Doménech et al, 2000;Cepriá et al, 2007), these signals are attributable to the reduction of mercury sulfide:…”

Application of Modified Tafel Analysis to the Identification of Corrosion Products on Archaeological Metals Using Voltammetry of Microparticles

“…In the first scan, peaks at + 0.65, + 0.45, + 0.20, À0.12 and À0.60 V were recorded. The two first peaks correspond to the Ag(I)/Ag(0) couple for silver ions in solution, as judged upon comparison with voltammetry at graphite electrodes immersed into AgNO 3 solutions, while the peak at + 0.20 V can be attributed to the reduction of a silver compound, possibly, silver acetate [61][62][63] or silver oxide [74]. This last, although only occasionally, accompanies silver sulfide in corrosion under determined conditions [75].…”

“…0.0 V and silver at + 0.45 and + 0.20 V, all frequently exhibiting peak splitting. Silver stripping peaks at + 0.20 and + 0.45 V have been attributed to the oxidation of silver to solid Ag(I) forms, silver acetate in the case of the peak at more positive potential [61][62][63]. The splitting of stripping peaks can be interpreted on the basis of the studies of Scholz et al on lead oxides [64,65], silver halides and silver sulfide [66,67], in terms of the oxidative dissolution of different metallic deposits.…”

The Use of Metal Nanoparticles to Produce Yellow, Red and Iridescent Colour, from Bronze Age to Present Times in Lustre Pottery and Glass: Solid State Chemistry, Spectroscopy and Nanostructure

“…Another approach has become popular, namely the study of modern replicas, prepared at the laboratory [42,43,47,49,96,97] or better by modern potters using gas firing [98]. This point will be discussed further.…”

“…A great effort has been made in the last few years to understand the different steps involved in lustre production by means of replica preparation [42,43,47,49,[96][97][98] and the comparison of the achieved microstructures with those of artefacts produced at different periods in various workshops. However, it is obvious that modern techniques of firing are different from the older ones, especially regarding the heating fuel and duration of thermal cycles.…”