Understanding the guiding formulation principles behind the use of natural cement in the 19th and early 20th centuries allows better interpretation of the results of laboratory analyses and more accurate reproduction of historic masonry and concrete materials. This paper reviews traditional formulation practices for natural cement mortars, grouts, stuccos, concretes, and lime-washes, including ingredient selection, technical and economic criteria affecting formulation, and how the materials and formulations changed over time. Effects on performance of typical formula variations are reviewed, and potential effects on performance of modern admixtures are considered.