Shelomo Dov Goitein writes, “the dichotomy of the kitchen into a meat and a milk section, so basic in an observant Jewish household, is … never mentioned in the Geniza."[75] Goitein believed that in the early Middle Ages Jewish families kept only one set of cutlery and cooking ware. According to David C. Kraemer the practice of keeping separate sets of dishes developed only in the late 14th or 15th centuries.[76] In earlier times, the household's one set of cooking ware was kashered between dairy and meat (and vice versa).[77] Alternatively, users waited overnight for the meat or dairy gravy absorbed in a pot’s walls to become insignificant (lifgam) before using the pot for the other species (meat or dairy).[78]