In mid-late Yuan dynasty, trading with East and West Asia was facilitated by China’s territorial expansion. Trading goods such as high quality cobalt compounds provided Ching-Te-Chen, the center of Chinese ceramics industry, an important pigment for coloring. This not only established the significance of underglaze-blue wares, but also opened the door to porcelain export in Yuan dynasty. 

Everted rim. Five layers of decoration from the exterior inwards include billows, peony scrolls, lotus scrolls, and inverted lotus petals with Buddhist emblems. 

Made of sturdy clay, this dish is decorated with imported indigo-blue pigment with bluish black iron rust. 

Transparent glaze with a tinged of blue.

Bottom unglazed area seems rough and sandy with obvious whirl tool marks at center. A closer look shows coarse and loose clay quality along with lots of impurities, sand holes, and iron rust.

Large wares in Yuan dynasty were colored primarily using imported cobalt pigment producing radiant shades of blue. Ferric oxide in the imported pigment has led to the formation of deeply embedded brownish black iron rust around areas where pigment accumulates.

This iron rust is greenish brown around its edges and appears slightly more depressed than the surrounding surface.Penetrating spots of blue on the surface of the glaze are remains of non-melting impurities after fire.