The azulejo's blue starts as dull grey
The azulejo's blue starts as dull grey. Cobalt oxide only turns deep blue in the kiln, and each Porto tile is fired twice, once for the body, once for the glaze.
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The azulejo's blue starts as dull grey. Cobalt oxide only turns deep blue in the kiln, and each Porto tile is fired twice, once for the body, once for the glaze.