Compositional classes and diversity in archaeological ceramic studies

Archaeological studies are based, at a large extent, on the study of the materials that form the different unearthed assemblages. Thus, ceramic assemblages are defined by their compositions, i.e. how many pots of different types do we have. Those assemblages, are supposed to shed light on chronological issues, as well as on social issues related to the social context after which they were formed. Therefore, one of the key problems in Archaeology is the formation of the archaeological record, since any study based on the unearthed evidence will be thus necessarily conditioned. Pottery, as many other types of artefacts, rarely appears as complete vases. The activity in the systemic context (in the living societies of the past), and the activity in the archaeological one usually leads to incomplete vessels, represented by an unknown number of isolated shards. Several strategies have been proposed to overcome these problems, and they are collectively known as quantification studies (Orton, 1993). In such studies, reassembly of shards is conducted up to different extents. Besides, different principles are assumed in different quantification methods. Even so, especially in studies not devoted to pottery, some criticism have been made on the concept of taxonomical abundance, which guides quantification studies, highlighting the underpinning role of taphonomical issues (Lyman, 2004). Moreover, individuals and assemblages are in the basis of any archaeometric study, and sampling is the most crucial derived issue (Orton, 2000)

Identificació arqueològica i arqueomètrica de noves produccions de Terra Sigillata Hispánica a l'àrea dels Pirineus catalans

Les excavacions realitzades a la Cerdanya han proporcionat l'evidència arqueològica de la possible existència d'una producció local de TSH, que inclou les formes tradicionals i d'altres formes noves. Per tal de contrastar aquesta hipòtesi, s'ha desenvolupat un estudi arqueometric per FRX i DRX. Els resultats mostren l'existència de diverses produccions desconegudes fins el present, sense que cap dels materials estudiats hagin pogut associar-se al taller d'Abella ni a les produccions de l'àrea de Tricio. Aquestes noves produccions ofereixen, a més, una important diversitat tecnològica.Archaeological research in the area of Cerdanya has provided archaeological evidence to postulate the existence of local production of HTS. This production includes traditional types, but also new ones. In order to examine this hypothesis an archaeometric study has been undertaken by means of XRF and XRD. The results show the presence of different productions yet unknown to present. Moreover, none of the studied materials have been successfully related with Abella workshop, neither with the products from Tricio. These new productions exhibit an important technological diversity

Alterations of Na, K and Rb concentrations in Mycenaean pottery and a proposed explanation using X-ray diffraction

One of the most important reference groups for Mycenaean pottery is the Mycenae/Berbati (MB). In several studies, a second group has been identified (MBKR). The chemical compositions were similar to MB, but with important differences in the Na, K and Rb contents. The present study suggests that these differences are due to selective alteration and contamination processes that are indirectly determined by the original firing temperature. Therefore, groups MB and MBKR should be considered as a single reference group

Morphometrics and compositional classes. The stuy of anthropomorphic sculptures from Teotihuacan (México)

Morphometry is defined as the measurement of the external and perceptible characteristics, i.e., in a first approximation, of the shape or morphology of an object. It includes information related to the object’s appearance as well as to its physical and diachronic constitution (Verrecchia, 2003). Morphometric studies attempt to describe this form or shape through mathematical relationships that allow numerical data, and this can be achieved in different ways. In general, tow main types of analysis can be performed whether they are or they are not based on the study of the contourn. In several instances, the actual contourn is not supposed to be really informative. Instead, elementary Euclidean geometrical measurements or the definition of significant points (landmarks or semi-landmarks), referenced in coordinates systems, are used

Mathematics, statistics and archaeometry: the past 50 years or so

This review of developments in the use of mathematics and statistics in archaeometry over the past 50 years is partial, personal and 'broad-brush'. The view is expressed that it is in the past 30 years or so that the major developments have taken place. The view is also expressed that, with the exception of methods for analysing radiocarbon dates and increased computational power, mathematical and statistical methods that are currently used, and found to be useful in widespread areas of application such as provenance studies, don't differ fundamentally from what was being done 30 years ago

Exploring the technique of glazing used by the potters of Barcelona

The application of glazes on pottery became common in Western Europe from the late 12th century / early 13th century onwards. However, the process of 'glazing' entails different degrees of complexity which might involve a great variety of raw materials. Accordingly, simple glazing process consists of a single layer applied over the surface of the body, becoming a shiny and transparent coat after firing. The addition of pigments would result in a coloured glaze that can be translucent or even opaque. The more complicated sequence occurs in decorated glazed pottery, where opacifiers, pigments and metals are added to produce an opaque white glaze to enhance the decoration. This glaze is applied to the bisque pottery and manufactured, usually, in a second or third firing. To deepen our knowledge of the glazing technique, we have studied glazes from coarse pottery, cooking ware, polychrome coarse pottery and majolica from Barcelona (13th to 18th centuries AD). The application of the glaze, the thickness, and the composition of glazes (including opacifiers, pigments and/or metals) have been examined, through Scanning Electronic Microscopy (SEM). This study has revealed the high diversity in the glazing technique

The case of Black and green tin glazed pottery from Barcelona between 13th and 14th century: analysing its production and its decorations

Black and green tin-glazed pottery is known to be one of the true majolica manufactures at Barcelona during the end of the medieval period. This pottery means the evolution of a production process for achieving opacified decorated tableware, started one century before, with the elaboration of what is known as archaic majolica. Black and green implies a new high variety of decorative motifs made in black, or in black and green, on a white opacified glaze prepared following a recipe adapted by potters to prepare the base glaze and to applicate the pigments for attaining the decorative patterns, characteristics of this period. Originally thought as imported from Valencia workshops, the development of different archaeometric projects conducted in the core of the ARQUB team, allows verifying an origin in Barcelona. Besides, recent excavations dated back to the 14th century provided a great number of Black and green sherds with new decorative motifs unknown up to now, allowing the specialists to create a new corpus of decorative patterns, which is still in progress. Based on insights obtained from those first archaeometric studies and considering the advances on the classification of decorations based on archaeological arguments, a new sample of Black and green sherds was selected for this study. The aim was to observe whether decoration and technique of manufacture could in some way be related, understanding the technical process as the selection and application of raw materials and the firing temperature at which this pottery was made. To achieve these objectives, X-ray fluorescence (XRF), X-ray diffraction (XRD), and Scanning Electronic Microscopy (SEM-EDX) have been performed. The results allow verifying the groups previously defined and to identify a new chemical group, probably related to a recipe for the body-paste different from the others. On the other hand, the study enabled us to observe differences also in know-how in firing, which in some cases seem to be connected with differences in the decorative motives, suggesting, perhaps, the discrimination of artisans