Red Brick Dust

Red brick dust is fired red brick reduced to powder. In hoodoo, the African American folk magic of the southern United States, it is in common use against evil: laid at the entrance of a home, it is meant to clear evil away and to protect the household from it. The brick it comes from is a fired clay building brick. Its raw materials are clay and shale, themselves formed over thousands of years as rocks such as granite weather and break down; one proposed mix is half to three-fifths silica sand, a fifth to three-tenths clay, a little lime, up to seven per cent iron oxide and a trace of magnesia. The clay is ground, mixed with water, shaped and baked in a kiln, at around 900 to 1,000 °C for moulded bricks, which makes the brick hard and long-lasting. Its colour depends on what the raw materials contain, how hot the kiln runs and the air inside it. Most clays burn to shades of red, deepening to dark red and purple and finally to brown or grey as the heat rises towards 1,300 °C, while a high iron content gives pink bricks and a high lime content white or yellow ones.