Message:

<p>[QUOTE=&quot;2manybooks, post: 12126962, member: 8267&quot;]Cobalt oxide (the mineral used to create the underglaze blue) is black when first applied, turning blue only during firing. Some combination of the absence of the glaze in that area, the concentration of the cobalt oxide used, and the firing conditions may have resulted in the original black application remaining visible. So, not an &quot;underdrawing&quot;.[/QUOTE]</p><p><br /></p>

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