Research paper Evaluation of archeothermometric methods in pottery using electron paramagnetic resonance spectra of iron G.M. Mangueira a , R. Toledo a , S. Teixeira b , R.W.A. Franco a, ⁎ a Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense (UENF), Av. Dr. Alberto Lamego, 2000, CEP: 28013-602 Campos dos Goytacazes, RJ, Brazil b Laboratório de Estudo do Espaço Antrópico, Universidade Estadual do Norte Fluminense, Av. Dr. Alberto Lamego, 2000, CEP: 28013-602 Campos dos Goytacazes, RJ, Brazil abstract article info Article history: Received 5 December 2012 Received in revised form 4 October 2013 Accepted 7 October 2013 Available online 6 November 2013 Keywords: Archeological pottery Electron paramagnetic resonance Firing temperature Fe 3+ Archeothermometry Archeometry Knowing the techniques mastered by ancestors in their production of pottery can help understand their habits and skills, therefore increasing the understanding about their culture. In this work, we study pottery from an archeological site located in the city of Campos dos Goytacazes, state of Rio de Janeiro, Brazil, in order to appraise the firing temperature, atmosphere and time during pottery production. For this purpose, electron paramagnetic resonance spectroscopy (EPR) is used to analyze the signals of iron (Fe 3+ ). Methods for obtaining the firing temperature were assessed, comparing archeological pottery with clay and changes caused by heat treatment in archeological pottery. In addition, potteries were prepared in laboratory, finding changes in the EPR spectra resulting from changes in the parameters of pottery making. The observation of colors profiles can provide information about temperature, time and firing atmosphere, but it is not accurate. From these findings, it was considered that the archeological pottery studied were prepared in a single firing, at temperatures up to 650 °C in an open pit firing with semi-oxidizing atmosphere during a short time of approximately 0.5 h. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The study of production methods of archeological pottery (AP) can provide important information about the culture of ancient peoples that inhabited in a particular region. In some cases, the most accurate information about a civilization comes from archeology, through the study of materials produced by the ancestors. Aspects related to the preparation of archeological pottery, such as the materials used, temperature, atmosphere and time of firing allow the identification of social groups (Kirch, 2004). Conceptually, archeology deals with the dimensions of space and time for analysis and interpretation. One conceptual category is the notion of tradition, defined as a group of elements or techniques with temporal persistence. Traditions can be divided into stages, which are sets of cultural elements that describe local aspects of any tradition, which may be pottery, lithic, or housing standards, related to time and space in one or more places (Prous, 1992). AP samples analyzed in this study were donated by the History Museum of Campos dos Goytacazes and they are from the archeological site of Caju (RJ-MP-8) (Dias, 1997). During excavation in the 1980s, the materials collected were dated by Carbon-14 method as being between 800 and 1500 years old, and classified as belonging to Una Tradition from the Mucuri phase (Dias, 1997). Una Tradition spread from central Brazil to the coast between the Una and Paraíba do Sul Rivers, lasting about 2000 years (Fausto, 2005; Prous, 1992). The Mucuri phase (Dias, 1997) was identified through the pottery artifacts, which are normally produced by a technique known as spiral coiling, which consists of making rolls of clay and their subsequent superposition in order to make vessels. The wall formed by the rolls is pressed and the vessel is smoothed in order to reduce undulations caused by the method and also to make thickness homogeneous (Lima, 1987; Prous, 1992). The high plasticity of clay mass can cause deformation of the parts during the drying and fissures during firing. In order to make them more resistant, it is common to add certain substances, named temper, which can be organic or inorganic substances (Lima, 1987). In pottery characterized as Una from the Mucuri phase, most common substances used were grains of quartz or feldspar. The smoothing of the parts is frequent in order to fix the roughness produced by the grains. Decorations as painting or roughness are not usually seen. The fragments under study are parts of a set of funerary urns (Dias, 1997), which in this site have the form of monkey pot fruit (known as ‘sapucaia’ in Brazil)(Lecythis ollaria)(Prous, 1992). This particular type of pottery is very convenient in order to study the firing temperature, because it retains the characteristics of initial firing as it is not reheated later as pottery used in cooking. The aim of this study was to make pottery with thickness and color profiles similar to that of AP. Subsequently, methods for estimating the firing temperature were tested in this current pottery (CP) and data were compared to data from AP. The methods for estimating the firing temperature of archeological materials (archeothermometry) using electron paramagnetic resonance (EPR) consist of monitoring the intensity and area of Fe 3+ signals and the effects of heat treatments. The relative areas of Fe 3+ (EPR spectra) Applied Clay Science 86 (2013) 70–75 ⁎ Corresponding author. Tel.: +55 22 27486497. E-mail address: franco@uenf.br (R.W.A. Franco). 0169-1317/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clay.2013.10.008 Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay