A heavy soil, composed largely of clay and silt in sufficient quantities to form a matrix in which sand particles are firmly imbedded; water is added, and straw, manure, and fragments of tile are sometimes combined with this mixture to provide increased mechanical strength and cohesion when it dries. It can be used as a plaster or be formed into bricks, often shaped by hand in a wooden form, then sun-dried; widely used in Spanish Colonial architecture and its derivatives. Adobe brick walls are often lime-plastered to improve resistance to weather; a coating such as slaked lime acts as a stabilizing agent.