Earthen plaster

Earthen plaster (adobe plaster, dagga) is a blend of clay, fine aggregate, and fiber. Other common additives include pigments, lime, casein, prickly pear cactus juice (Opuntia), manure, and linseed oil. Earthen plaster is usually applied to masonry, cob, or straw bale interiors or exteriors as a wall finish. It provides protection to the structural and insulating building components as well as texture and color.

All plasters and stuccos have several common features: they all contain a structural component, a binding element, and some form of fiber. Usually the term plaster refers to a wall covering made from earth, lime or gypsum, while stucco uses a cement or synthetic binding element.

Clay is a soil component consisting of extremely fine particles. Most clays consist of hydrous aluminum silicates, though there is a considerable amount of chemical variation among the clays. Clay is cohesive and binds to the sand and the straw, holding the mixture together, as well as securing the mixture to the wall. Clay is also plastic when wet, which makes the plaster mixture workable.

Sand provides structure, strength, and bulk to earthen plasters. Sand consists of tiny mineral granules of rock, its parent material. Predominately composed of silicon dioxide (quartz), sand is a non-reactive substance. Because sand occurs naturally in many subsoils, all of the sand necessary may be already found in the soil.

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