A non-destructive technique for measuring ceramic porosity using liquid nitrogen Karen G. Harry a, ) , Allen Johnson b a Department of Anthropology and Ethnic Studies, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 455003, Las Vegas, NV 89154-5003, USA b Department of Chemistry, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 4003, Las Vegas, NV 89154-4003, USA Received 6 January 2004; received in revised form 25 March 2004 Abstract Because porosity can affect a wide range of performance attributes in vessels, its measurement has become an important component of ceramic technological studies. To measure ceramic porosity, archaeologists have borrowed well-established methods from the material sciences. However, these methods can have drawbacks for archaeological applications including the potential to damage archaeological residues contained within the sherd, the need for expensive equipment, and/or the use of hazardous materials. In this paper we introduce a new, non-destructive method for measuring porosity based on the infusion of liquid nitrogen into the sherd. A comparison of results obtained from this method with those obtained from other approaches indicates that the technique produces reliable results. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Porosity; Ceramic technology; Materials characterization; Liquid nitrogen; Physical methods 1. Introduction Porosity is a fundamental attribute of ceramics. As such, its measurement plays an important role in archae- ological interpretation. There are two research arenas for which porosity may have behavioral relevance. First, it can inform on aspects of archaeological manufacturing technologies. A variety of factors, including initial firing temperature, the type of clay and tempering materials used, and the manufacturing and forming techniques employed all contribute to the degree of ceramic porosity exhibited. Second, the attribute may inform on use- related properties of the ceramic. Ceramic engineering principles [10,15,23,25,27] and modern archaeological experiments [25,28] indicate that a wide range of per- formance attributes is affected by the amount of pore space present in a ceramic body. Such attributes include vessel strength, permeability, thermal insulation, abra- sion resistance, and resistance to thermal shock. Past archaeological studies of ceramic porosity reflect these research concerns. Porosity measurements have been used to develop inferences regarding the initial firing temperatures of ceramics [19,24,35], to identify functional classes of wares [18], and to evaluate the differences and similarities between manufacturing tech- nologies and/or clay sources used in ceramic production [6,13,27,32]. Other studies have relied on porosity measurements (often in conjunction with other techno- logical attributes) to examine how porosity might have improved or degraded vessel function [14,30,33], while still others have examined how potters might have altered manufacturing techniques to increase or decrease vessel porosity [16,17]. Techniques to measure the porosity of archaeological ceramics have been largely borrowed from the material sciences. Most archaeologists have relied on methods that impregnate the pores with water, although other techniques have been used as well. These different meth- ods, however, have a variety of drawbacks for archae- ological applications, including the potential to damage either the sherd or the organic residues contained within the sherd, the need for expensive or specialized ) Corresponding author. Tel.: C1-702-895-2534. E-mail addresses: karen.harry@ccmail.nevada.edu (K.G. Harry), aljohnson@ccmail.nevada.edu (A. Johnson). Journal of Archaeological Science 31 (2004) 1567e1575 http://www.elsevier.com/locate/jas 0305-4403/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2004.03.020