Synthesis of Large Platelets of Egyptian Blue via Pseudomorphosis after NaRUB‐18

A colored platy substrate with appreciable aspect ratio can improve the hiding power while extending the color range of pearlescent pigments. One of the oldest synthetic pigments, Egyptian blue, possesses a layered structure and a platy morphology, making it a promising colored substrate for pearlescent pigments, which derives its blue color from Cu II . Unfortunately, existing synthesis routes are either not technically benign or lack the natural platy morphology. Here, we introduce a new synthesis route starting with large, square‐shaped platelets of a synthetic layered sodium silicate (NaRUB‐18). As evidenced by Rietveld refinement and scanning electron microscopy, NaRUB‐18 can be converted with conservation of this attractive morphology (pseudomorphosis) into Egyptian blue.