In the Neolithic period, inhabitants of the Greek island of Crete coated their walls with clay plaster, a finish with a malleable texture that was ideal for carving decorative relief designs. Beginning as early as 900 A.D., the ancient Pueblo people of the American Southwest slathered the exterior walls of their dwellings with adobe (sun-dried clay) to protect them from moisture, fire, and pests. Praised for its rich tones, the way it warmly reflects light, and its ability to absorb and release humidity, clay plaster has been used to finish walls across the globe for centuries. Today, thanks in part to its beauty and malleability, the finish is embraced as a sustainable alternative to standard paint.
Traditionally, the components of clay plaster are clay, sand, water, and fiber. Over time, additional additives like wheat-flour paste, manure, cactus juice, and casein were added to make it more durable and workable. Unlike most paints, clay plaster has a low environmental impact: It is nontoxic, contains no volatile organic compounds, and it isn’t heated to high temperatures in production. When applied properly, it is also mold-resistant, breathable, and as Noel Adams of Traditional Natural Plaster Company (www.traditionalplaster.com) in Portland has seen time and time again, fairly easy to repair. “My son loves to bang the rocking chair against the wall and create dents,” he says. “In minutes I can just re-wet it and re-trowel it and the damage is gone.” The son of a traditional plasterer, Adams discovered earthen plasters (which include clay, gypsum, and lime) in 2003, and he has since applied a variety of recipes to the walls of over a hundred homes around Portland. What follows is Adams’s simplest technique for the novice plasterer.