## 2 Materials and Methods
### 3D Photogrammetry  
Three-dimensional models were created through the Structure-for-Motion technology based on the capture of photos of an object and the subsequent processing of the images \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Parameters** & **S1** & **S2** \\ \hline \multirow{4}{*}{**CAMERA**} & ISO & 100 & 100 \\ \cline{2-4}  & Focal length & 50 & 70 \\ \cline{2-4}  & Aperture (f/stop) & \(1/16\) & \(1/16\) \\ \cline{2-4}  & Exposure time & \(1/160\) s & \(1/160\) s \\ \hline \multirow{2}{*}{**FLASH LAMP**} & Power & \(1/16\) & \(1/16\) \\ \cline{2-4}  & Flash time & \(1/4255\) s & \(1/4255\) s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The camera and flash lamp parameters used for each artefact shooting session are reported. using the Agisoft Metashape software (v1.8.0). The initial step of image acquisition was crucial, as the accuracy of the 3D model is contingent on the photo quality. The shooting session was performed using a Canon EOS RP camera fixed on a Manfrotto 055 PRO3 tripod. The camera was equipped with an RF 24-105 mm IS STM lens, a CMSO full-frame 26.2 megapixel sensor, and a camera remote for the shutter control. Samples were set on a rotating platform through a piece of kneaded eraser, which did not cause surface alteration and is widely employed in archaeological research [58; 59] because it preserves the artefacts from damage while guaranteeing stability during experiments. As visible in Figure 3a, markers directly provided by Agisoft Metashape software (Tools < markers < print markers) must be fixed close to the sample as reference points for the subsequent image processing; with the same intention, a short sequence of letters was stuck onto the lateral surfaces of the kneaded eraser. The correct homogeneous illumination of the sample surface was ensured by a white background and two fluorescent studio lamps (Fotobestway ES-755), set at approximately 45\({}^{\circ}\) relative to the plane on which the object was placed. A ColorChecker X-RITE was employed for the eventual colour correction of an entire shooting file. The camera shooting parameters and the camera-object distance were calculated using the online software DoFmaster ([[https://www.dofmaster.com/dofs.html](https://www.dofmaster.com/dofs.html)]([https://www.dofmaster.com/dofs.html](https://www.dofmaster.com/dofs.html)) (accessed on 11 March 2024), inserting the measurable depth of the object and the chosen camera focal length. Table 3 reports the overall number of photos captured for each sample along with the specific camera setting parameters, which must be maintained at a constant value during the entirety of the photographic session. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **R5** & **R3** & **R2** & **R4** & **R1** \\ \hline
**ISO** & 400 & 400 & 400 & 250 & 400 \\ \hline
**focal length** & 105 mm & 105 mm & 105 mm & 105 mm & 105 mm \\ \hline
**f/stop** & f/22 & f/22 & f/25 & f/22 & f/25 \\ \hline
**Shutter speed** & 1/25 s & 1/25 s & 1/30 s & 1/25 s & 1/25 s \\ \hline
**Camera-object distance** & 96.4 cm & 94.6 cm & 60 cm & 80 cm & 90 cm \\ \hline
**Overall photos** & 257 & 248 & 193 & 273 & 279 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The camera parameters used for the shooting sessions related to each sample are reported. Figure 3: (**a**) The sample R5 correctly positioned within the designed set for the shooting session; (**b**) Schematic representation reporting the steps involved in the Agisoft metashape workflow to create one chunk of the R2 three-dimensional model. Every sample required two different photo shooting sessions, in which all the aforementioned reference points (markers and sequence of letters) needed to be changed; the first session differed from the second one by 180\({}^{\circ}\) rotation of the sample around its horizontal axis. Each session comprised three series of photographs, captured at 0\({}^{\circ}\), 45\({}^{\circ}\), and 60\({}^{\circ}\) relative to the horizontal plane on which the sample was placed.