Stucco is a fine plaster used as a coating for walls or for decoration. It may be used to cover less visually appealing construction materials such as concrete blocks, steel, or adobe. Modern stucco is made of sand, water and Portland cement. Some craftsmen add lime, others consider it improper. Sometimes additives such as acrylics and glass fibers are added to improve the structural properties of the plaster as well as its workability.