## 1 Introduction  
The firing temperatures of ancient and historic ceramics are important to archaeologists as indicators of developments in firing technologies, kilns, and ceramic production. This field of study has been termed _archaeothermometry_[1; 2; 3]. Interpretations are complicated because porosity is affected by the raw material choices of potters, the rate of temperature rise, the time maintained at peak temperature, the rate of cooling, the total duration of firing, and the conditions during firing (oxidizing, reducing, or mixed). Therefore, analysts usually propose an upper range rather than a precise temperature [4; 5]. Current methods for estimating firing temperatures of archaeological ceramics are often problematic [6] and firing-temperature studies tend to be less common in the archaeological literature compared to other research goals. Micro-computed tomography (micro-CT) combined with 3D image analysis to study pore systems in archaeological ceramics is a promising approach for investigating firing temperatures and firing effects on microstructures and on the functional properties of ceramic materials. The initial research presented here is intended to provide a base for further investigations that will help expand the tools and approaches available to archaeological scientists. The most common current approach to estimating ceramic firing temperatures is to study the mineralogy of archaeological sherds. Techniques such as thin-section petrography, scanning electron microscopy, X-ray diffraction, FTIR spectroscopy, or thermal analysis methods are often employed to study the degree of vitrification of the ceramic matrix, changes in minerals known to decompose or alter at certain temperatures, and the presence of minerals that form in ceramic materials at high temperatures [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. Sometimes, sherd fragments are refired in the laboratory and any changes in mineralogy and microstructure at specific temperatures are noted [20; 21; 22; 23; 24]; the appearance after incremental temperature increases is compared to the original sherds to identify the point at which the original temperature has been exceeded [25; 26]. Alternatively, potential raw materials are fired at incremental temperatures and the material transformations are studied [25; 27; 28]. Another approach is to use thermal expansion measurements to estimate firing temperatures [2; 29]. These methods can be problematic. Experimental firings used for temperature estimations may not match actual firing temperatures [30], and a complex array of variables can affect ceramic microstructure and appearance [6]. Measurements of total open porosity are also used to estimate firing temperatures [20], with lower percentages tending to correspond to higher firing temperatures [31]. As the temperature rises, the clay matrix begins to sinter and vitrify, causing pores to shrink [1; 32] and a decrease in open porosity with a higher proportion of isolated and closed pores [33]. The size and shape of pores are also affected by a combination of raw materials and firing temperatures. For example, lower-fired wares may have added organic material that burns out or carbonates that decompose leaving large irregular pores, whereas fine-grained materials fired at high temperatures may develop small, rounded pores [1] (Figure 1). A few experiments have looked at changes in pore size and homogeneity with temperature, and they have found that higher firing temperatures tend to result in a more homogeneous system of pores and a smaller average pore size [34]. Other experiments have shown that the amount, size, and shape of pores in a ceramic body can be an indication of the degree of vitrification and thus of firing temperature [35]. [PERSON] et al. [33] note that pore topology is a key variable in understanding ceramic firing technology and its effect on pore morphology and pore orientation during thermal expansion, sintering, and vitrification processes.