Abstract New archaeointensity results were obtained from 14 groups of baked-brick fragments collected in and around Pisa (Tuscany, Italy). The fragments were assembled from civil and religious buildings whose dating of construction or renovation, over the past millennium, was constrained by documentary sources. This collection, analysed using the Triaxe protocol, was found particularly suitable for intensity experiments, with a success rate of c. 84% corresponding to 276 fruitful specimens associated with 125 independent brick fragments. The Tuscan data clearly show a peak in intensity at the transition between the sixteenth and seventeenth centuries. They are also in very good agreement with, and complementary to, a dense dataset previously obtained in France. Considering the results available within a 700 km radius of Beaune (between Paris and Pisa), all satisfying a set of quality criteria, a mean geomagnetic field intensity variation curve was constructed for the past millennium using a newly developed transdimensional Bayesian technique. This curve, which thus incorporates the new Tuscan results, allows a better recognition of three intensity peaks (during the twelfth century, the fourteenth century and around AD 1600) in western Europe. The detail of this curve is a clear illustration of the centennial-scale resolution that can be achieved using accurate archaeointensity data.

Abstract In this paper we present bulk X-ray fluorescence-X-ray diffraction (XRF/XRD) and microanalytical scanning electron microscope-electron microprobe analysis (SEM-EMPA) data on historical bricks from Medieval or Renaissance buildings of Ferrara (NE Italy) to provide insights into the nature and provenance of the raw material as well as clues on the sintering techniques. Chemical data indicate that the starting materials were obtained by mixing high Cr-Ni clay and subordinate sand (both quarried from the Po river alluvial deposits) with the possible introduction of a Na-rich flux component. Thin-section observation, XRD and micro-analytical data indicate the presence of key accessory phases such as pyroxene, amphibole, epidote and rare olivine in the pre-fired mineral assemblage, confirming the utilization of the Po river sediments. Recognition of neo-formation firing phases (e.g. melilite, wollastonite), together with composition of micas, amphiboles and interstitial glasses, indicate kiln temperatures between c . 800 and 1000 °C. This provides guidelines for making new compatible and durable bricks to be utilized for restoration, and contributes to the preservation of historical masonry.

Abstract Clay has been used in a wide range of ceramic products for thousands of years and continues to be a major component in most ceramic bodies today. Fiebinger (1997) states that the annual worldwide production of clay is nearly 400 million tonnes. In the top 50 ranking of extracted minerals and materials, clay is placed 8th with respect to quantity, and 19th in terms of value. Over 90% of the annual tonnage is utilized in the heavy or structural clay sector, with the remainder (predominantly ball clays and plastic clays) being used for higher quality or fine ceramic products. The value of the worldwide ceramic production (of all varieties) was estimated at US$ 113 billion in 2000 ( Reh 2000 ). From 1991 to 1999, growth was significant in the advanced ceramics, tile and sanitaryware sectors, but less so in structural ceramics and refractory products, as detailed below: • wall and floor tiles ; 70% growth with US$ 14 billion turnover in 1999; • advanced ceramics (including the carbon and graphite sector); 63% growth with US$ 40 billion turnover in 1999; • sanitaryware ; 50% growth with US$ 12 billion turnover in 1999; • structural ceramic sector (bricks, roofing tiles, pipes); 17.5% growth with US$ 23 billion turnover in 1999; • refractory products ; <10% growth with US$ 12 billion turnover in 1999. The technical definition of a ceramic product is ‘a product that is composed of polycrystalline, inorganic and non-metallic materials that have been subjected to a temperature of 540°C or more during manufacture or use’ ( O’Bannon 1984 ). In spite of the availability of modern, alternative products manufactured from plastic, steel, paper, glass-fibre/resin composites, borosilicate glass etc., the demand for ceramic products in all sectors remains relatively strong. This chapter describes how the chemical, physical and ceramic properties of the clay components have a predominant influence on the characteristics of both the unfired and fired product, and also considers the role and importance of the other body materials.