## 2 Materials and Methods
### Micro-CT Imaging  
Micro-CT imaging was performed with a Rigaku GX130 instrument (cone beam geometry). Samples from the ceramic sherds were set on the Styrofoam support of a horizontal holder. For this instrument, the sample holder remains stationary while the flat-panel X-ray detector (FPD) rotates around it 360\({}^{\circ}\) and at uniformly distributed viewing angles collects magnified projection images (micro-focus X-ray source to the center of \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Ceramic Type** & **Sherd Appearance** & **Firing Temperature** \\ \hline
1. & Southeast Kazakhstan, Late Iron Age, red-washed & 900 \({}^{\circ}\)C [31] \\  & earthenware & \\
2. & Southeast Kazakhstan, Late Iron Age, reduced & 1000 \({}^{\circ}\)C [31] \\  & earthenware, cream slip & \\
3. & Cambodia, Bangkong Kiln, 9 th–10 th C., Siem Reap, & \\  & stoneware & \\
4. & Cambodia, Torpchey Kiln 13 th–15 th C., Siem Reap, & \\  & brown-glazed stoneware & \\
5. & Gaoxian, Sichuan, China, modern workshop, coal & \\  & cinder-tempered, ash-glazed & \\
6. & Derge, Sichuan, China, modern workshop, black & \\  & graphite-rich clay & \\
7. & _Sancai_ glazed whiteware, Gongyi, Henan, China, & \\  & Tang Dynasty * & \\
8. & Yingjing, Sichuan, China, modern workshop, coal & \\  & cinder-tempered, ash-glazed & \\
9. & Xiba Kiln, Sichuan, China, Song Dynasty *, grey & \\  & stoneware with thick glaze & \\
10. & Dehua Kiln, Fujian, China, Song Dynasty *, & \\  & white-glazed porcelain & \\
11. & Celadon, Yaozhou Kiln, Shaanxi, China, Song Dynasty *, & \\  & green-glazed & \\
12. & Xing Kiln, Hebei, China, Song Dynasty *, & \\  & white-glazed porcelain & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Ceramic sherds studied with firing temperature ranges. rotation, 120 mm; W target; 7 Mp FPD with 116.424 \(\times\) 145.728 mm active area size; 49.5 \(\upmu\)m pixel size; 2352 \(\times\) 2944 pixels dimension; and 224 mm FPD to the center of rotation). To minimize image noise, each session began with a gain calibration to correct for any non-uniform responses of detector pixels to X-ray exposure, followed by a 57 min instrument warm-up period. Scanning time for each sample was also 57 min. Image noise was further reduced by ensuring that the samples were no more than about twice the size of the field of view used for imaging. All ceramics were imaged twice, once with a field of view of 10 \(\times\) 10 mm and again with 5 \(\times\) 5 mm. For both fields of view, the small focus spot size (5 \(\upmu\)m) was used for high resolution. Phase contrast and hence image quality were optimized with voltage and source intensity settings of 130 kV and 61 \(\upmu\)A, with a 0.06 mm Cu and 0.5 mm Al filter combination [66]. Three-dimensional reconstruction in the Rigaku software uses a filtered back projection reconstruction algorithm with a ring reduction filter. For fuller details on the instrument and settings, see Reedy and Reedy 2022 [51]. While the Rigaku GX130 has a nominal resolution of 4.5 \(\upmu\)m, the best actual spatial resolution achievable is 10 \(\upmu\)m, using a 5 \(\times\) 5 mm field of view and all settings optimized as described above. We checked this spatial resolution by imaging a micro-CT bar pattern (QRM) and confirming that the 10 \(\upmu\)m line and spot widths could in fact be accurately measured. Two samples of each of the twelve shends were first imaged with the field of view set to 5 \(\times\) 5 mm, giving a spatial resolution of 10 \(\upmu\)m, and then again with the field of view set to 10 \(\times\) 10 mm, giving a spatial resolution of 20 \(\upmu\)m. In previous work on brick porosity, the scans with 10 \(\times\) 10 mm field of view proved to be inferior to the 5 \(\times\) 5 mm field of view scans in characterizing the pore systems of historic and hand-made bricks and in differentiating different brick types [51].