Deep blue, fine particle, synthetic ultramarine pigment having rounded particles that are finer and more regular in size and shape than the natural ultramarine pigment. It is prepared by mixing anhydrous sodium sulfate or sodium carbonate with clay, silica, sulfur, rosin and charcoal then slowly heating in a reducing atmosphere. Variations in mixture proportions produce various shades of blue, green, violet and red pigments. The synthetic pigment is inexpensive and is used as an artist pigment in oil and watercolor, as a whitener in textiles and paper, and in wallpaper, soap, textile printing, and laundry bluing agents.
