## 3 Results and Discussion
### Bronze Mirror Exavated from Pit Tomb Ga-35 (No. 3)  
#### 3.3.1 Metal  
The sample showed selective corrosion on the \(\alpha+\delta\) eutectoid phase along the boundaries and cracks as thick layers of red and green corrosion materials. According to the bronze artifact corrosion layer classification system, this mirror was classified under the type II corrosion category [9]. The microstructure consisted of \(\alpha+\delta\) eutectoid and \(\delta\) phases, with scattered sulfide and lead particles (Figure 9a and Table 3).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Position**} & \multicolumn{8}{c}{**Element (wt\%)**} \\ \cline{3-8}  & & **O** & **S** & **Cu** & **Sn** & **Pb** & **Fe** & **Cl** \\ \hline \multirow{8}{*}{3} & 1 & 0.37 & \(-\) & 68.24 & 27.90 & 3.48 & \(-\) & \(-\) \\  & 2 & 0.49 & 16.12 & 78.26 & 2.58 & \(-\) & 2.55 & \(-\) \\  & 3 & \(-\) & \(-\) & 68.29 & 31.71 & \(-\) & \(-\) & \(-\) \\  & 4 & \(-\) & \(-\) & 72.17 & 27.83 & \(-\) & \(-\) & \(-\) \\ \cline{1-1}  & 5 & 5.67 & \(-\) & 6.98 & \(-\) & 87.35 & \(-\) & \(-\) \\ \cline{1-1}  & 6 & \(-\) & \(-\) & 100.00 & \(-\) & \(-\) & \(-\) & \(-\) \\ \cline{1-1}  & 7 & 4.33 & \(-\) & 90.07 & 4.79 & 0.34 & \(-\) & 0.47 \\ \cline{1-1}  & 8 & 17.86 & \(-\) & 79.94 & \(-\) & 2.20 & \(-\) & \(-\) \\ \cline{1-1}  & 9 & 3.87 & \(-\) & 55.67 & 35.28 & 5.18 & \(-\) & \(-\) \\ \hline \end{tabular}
\end{table}
Table 2: Ga-31 (No. 2) microstructure energy dispersive spectrometer (EDS) results.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Position**} & \multicolumn{8}{c}{**Element (wt\%)**} \\ \cline{3-8}  & & **O** & **S** & **Cu** & **Sn** & **Pb** & **Fe** \\ \hline \multirow{8}{*}{3} & 1 & 1.34 & 0.15 & 64.87 & 29.10 & 4.55 & \(-\) \\  & 2 & 1.24 & \(-\) & 68.37 & 27.73 & 2.66 & \(-\) \\ \cline{1-1}  & 3 & \(-\) & \(-\) & 66.51 & 33.49 & \(-\) & \(-\) \\ \cline{1-1}  & 4 & 0.73 & 23.91 & 60.13 & 0.60 & \(-\) & 14.63 \\ \cline{1-1}  & 5 & 7.13 & \(-\) & 8.50 & 1.61 & 82.76 & \(-\) \\ \cline{1-1}  & 6 & 13.22 & 6.81 & 2.06 & \(-\) & 77.91 & \(-\) \\ \cline{1-1}  & 7 & 5.12 & \(-\) & 94.88 & \(-\) & \(-\) & \(-\) \\ \cline{1-1}  & 8 & 17.51 & \(-\) & 8.59 & 66.95 & 6.96 & \(-\) \\ \hline \end{tabular}
\end{table}
Table 3: Ga-35 (No. 3) microstructure energy dispersive spectrometer (EDS) results.  
Figure 9: Ga-35 (No. 3) scanning electron microscope-energy dispersive spectrometer (SEM-EDS) images that show an uncorroded microstructure (**a**) and a line composed of secondary copper in the corroded microstructure (**b**).  
Because the bronze mirrors showed similar microstructures and distributions, they were most likely produced with the same techniques in a similar period. According to the ICP-AES analysis, a relatively small amount of Pb (0.85% to 1.10%) was detected, and all of them are ternary alloys of Cu-Sn-Pb (Table 4).  
In the Ga-35 (No. 3) bronze mirror, Pb and S appear to be present as lead sulfide, caused by the ore being added during the manufacturing process. Regarding the lead ore, previous studies on bronze production by-products excavated from the Wanju Sinpung ruins suggested that galena (PbS) obtained from southern Korean mines may have been used for smelting [15]. Sulfides were present in the bronze mirror's microstructures, but EDS detected only S or a combination of S and Fe. Secondary copper was found in clustered particles or lines, and twins were observed in some secondary copper (Figure 10).