Cobalt Blue Pigment / Azure Blue

Azure Blue Painting Medium: Cobalt Blue Pigment

Already the ancient Egyptians knew how to manufacture the intensive blue painting medium cobalt blue that they used for their sky blue paintings as well as for some mural paintings in their tombs with ceilings of painted stars in a night sky. Since the Middle Ages cobalt blue pigment was used as "royal blue" or some time later also as "azure blue" for fresco paintings and in fine arts on panels and canvas.
 

To manufacture cobalt potassium silicate, also well know as "smelt", the traditional way, you have to heat cobalt oxide, quartz sand and potash up to more than 1000°C.

During this procedure you get a blue mass of molten glass (smelt, ~melting). Then you have to rinse this just created cobalt potassium silicate glass with cold water until it will shatter into many small pieces of broken glass.

 
Those small pieces have to be crushed, pulverized and finally watered in a muddy bath. This process creates from pulverized cobalt glass an azure blue artists paint smelt, that you can be used to stain glass objects or as a fireproof glaze. Royal blue pigments played a major part in early glass designs and glass paintings.
 

Since the Middle Ages cobalt blue was used to paint or decorate the walls of houses inside and outside. Especially as outside colour, these pleasant azure blue pigments have proven long lasting luminosity, colourfast quality and durability.