In the Southwestern United States, adobe buildings comprise a significant portion of our architectural heritage. The recognition of this fact has led to research to devise better methods to preserve buildings constructed of adobe, however, many of the new methods are not appropriate for buildings in-use or are to costly to implement in communities or organizations with limited means. In an effort to devise cost-effective preservation methods based on traditional plastering techniques, aged plasters of varying durability have been analyzed using modern materials characterization techniques in order to determine what factors lead to durable plasters. In addition, the laboratory work has been supplemented by oral histories and practical experience in the field.