This literature review on the subject of Roman pottery making covers studies done as early as 1945 and as recently as 1980. Maggetti draws several conclusions from these studies. Roman potters not only distinguished between the various chemical and mineral components of the layers of earth, but selectively and methodically used certain types of soil in their pottery production. Furthermore, the potters' knowledge of the soil composition was the result of deliberate and scientific studies of the soil. Evidence has also been found that indicates the importation of certain soil types not native to the region; the potters apparently sought out soil possessing certain qualities from other locales.