Retrieving "Valence State" from the archives

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1. Pottery

   Linked via "valence state"

   Atmospheric Effects on Color
   The color of unglazed, fired clay is primarily determined by the presence and valence state of iron oxides ($\text{Fe}2\text{O}3$ or $\text{FeO}$) within the clay body.
   Oxidizing Atmosphere (Excess Oxygen): Iron oxidizes to $\text{Fe}^{3+}$, resulting in warm colors ranging from buff to red (terracotta). This atmosphere is critical for achieving the deep reds characteristic of Roman [terra sigillata](/e…