French and Spanish researchers have used the ALBA center synchrotron light Cerdanyola del Vallès (Barcelona) to decipher the history of blue and white Chinese porcelain from the Ming dynasty, from the 15th century, and have been able to determine, for example, that it was cooked between 1,250 and 1,300 degrees Celsius.
Is about porcelain decorated under the varnish with blue pigments based on cobalt and produced with a single firing at high temperatures.
The scientists have been able to identify the firing temperature by determining the pigments in the porcelain and the conditions of reduction-oxidation of the medium during its production.
According to the researchers, study method used could also be applied in a wide range of modern and archaeological ceramics to elucidate their production technology and hence deduct its seniority.
Precisely, study the many ceramic pieces that are usually found in most archaeological sites dating from the Neolithic, when the first human settlements appear, is one of the main challenges of archeology to reconstruct history of a place or period.
In this context, researchers have used the combination of two techniques characterization based on synchrotron light to study porcelains from the Ming dynasty.
The cobalt blue pigments used have varied origins and, for example, from 1279 to 1423 AD. They mainly used an iron-rich cobalt mineral imported from persia.
Its use caused characteristic dark spots iron-rich on the blue decorations, and later, when the use of manganese-rich Chinese cobalt ore spread, dark spots appeared rich in this chemical element.
In this work they have analyzed a fragment of a bowl large with numerous and visible dark spots, originating from the kingdoms of Chenghua (1464-1487 AD) and Hongzhi (1468-1505 AD) of the Ming dynasty and belonging to the Jiangxi area.
The researchers carried out experiments of X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF) in the Claesen light line of the ALBA Synchrotron for rastrear chemical variations in porcelain decorations associated with the development of dark spots.
The first author of the study is Professor Josep Roqué-Rossell, from the Faculty of Earth Sciences and the Institute of Nanoscience and Nanotechnology of the University of Barcelona, and CEME researchers from the University of Tolouse, the Museum of Natural Sciences of Barcelona and the ALBA Synchrotron.
The results obtained suggest that, during porcelain firing, iron and manganese ions diffused, moving from sites with higher concentrations to areas with lower concentrations.
During cooling, the ions crystallized in the form of the oxide minerals rhodonite and hausmannite-jacobsite, which are intermediate compounds, which helped to identify the temperatures reached during its production. In addition, the detailed study of iron with the XAS technique has made it possible to evaluate the record of reduction-oxidation in porcelain varnish.
Researchers have also been able to determine the terms oxidation levels achieved during the production of blue and white porcelain comparing the results obtained to those of the natural basalt as a calibration method.
Although the production of blue and white porcelain it dates back to the 7th century AD. C., was under the ming dynasty, who ruled in China between 1368 and 1644, when it began to produce and export on a large scale to Southeast Asia, West Africa, the Middle East and Europe