## 1 Introduction
Figure 1: Typical pore size, shape, and homogeneity of a low-fired organic tempered ceramic (**left**) versus a high-fired fine-sand tempered ceramic (**right**). Thin sections mounted in blue-dyed epoxy and viewed in plane polarized light. Porosity in archaeological ceramics is usually studied by thin-section petrography [16; 18], scanning electron microscopy (SEM) [33], water [1; 31] or liquid nitrogen absorption [36], or by mercury intrusion porosimetry (MIP) [34; 37]. Each method has advantages but limitations, and none include the entire pore system and range of pore sizes [38; 39]. The research presented here highlights how micro-CT combined with 3D image analysis has strong potential for archaeological ceramic pore studies. Micro-CT is non-destructive, so if it is performed first on a sample, that same exact sample can then be used for any of the other methods used to study porosity or to estimate firing temperatures. It would be especially useful to make a thin section after the micro-CT imaging and combine porosity characterization with a study of mineralogy and matrix vitrification. A second advantage is that, unlike thin-section petrography and SEM analysis, micro-CT images show the full 3D pore networks. Finally, unlike many other techniques, the 3D image analysis of micro-CT scans provides quantitative data on many pore variables while also providing qualitative visual data, so it is possible to examine exactly where on the sample specific results are located. [PERSON] [40] explored how micro-CT could be used to discern firing condition effects on ceramic materials. He notes that both particle packing and porosity features of the ceramic matrix are related to firing temperature, and that micro-CT can be used to study the total porosity of the ceramic material including closed and open pore systems. He used laboratory-made ceramic raw materials fired at temperatures ranging from 400-1000 \({}^{\circ}\)C and Early Medieval shreds from the Venetian Lagoon. He concluded that micro-CT imaging was a potentially useful approach to relate microstructure and pore distribution to firing temperature. [PERSON] et al. [33] also used pore characteristics observed in micro-CT images to deduce firing degree and conditions and found that firing temperatures and atmospheres affect pore shape and orientation. Micro-CT analysis of pores in archaeological ceramics has also been used for other goals, such as deducing fabrication methods or identifying total volume porosity [41; 42; 43; 44; 45; 46; 47; 48]; it is also used, sometimes in combination with 3D image analysis, to analyze the porosity characteristics of related materials such as modern manufactured ceramics [49], chicks [38; 50; 51], and concrete [52]. In the experiments presented here, the focus is on examining the effects of firing temperature on ceramic pore systems with the data available through 3D image analysis of micro-CT images. The results are also used to examine how firing effects on pore systems may change the microstructure in ways that could influence the functional properties of archaeological ceramics such as density, durability, mechanical strength, thermal conductivity, permeability, and diffusion. Out of 42 variables analyzed, 26 were significantly associated with firing temperature. These include total volume porosity (open plus closed); the volume fraction of pores accessible to any ceramic surface; the ratio of pores accessible to a surface versus pores confined to the interior; many variables related to pore size and shape; and a variety of variables related to the nature of pore connectivity which were collected from sparse and dense graphs of pore networks and from pore network models.