Petrographic analyses were made of 386 utilitarian pottery vessels from 23 dated components of 18 Early Woodland through early Fort Ancient period sites (ca. 1150 B.C.–A.D. 1300) in south-central Ohio. The analyses reveal that a significant percentage ( 11.6 percent) of the 386 vessels bear uncolored (i.e., unpigmented) pottery slips and washes, that these surface materials were common (>56 percent) among the 23 sampled components, and that they were produced throughout most of the examined prehistoric sequence, including the earliest Early Woodland, when pottery making began in the Midwest. In contrast, a literature review indicates that uncolored slips and washes are unrecorded for utilitarian wares in the prehistoric Eastern Woodlands, that both colored and uncolored slips are unknown for any ceramics of the Early Woodland period, and that colored slips or washes in the pre-Mississippian Midwest have been observed in only low frequencies. Electron microprobe analysis of seven sherds show the compositional similarity of the clays of slips to the clays of their associated vessel bodies, indicating that the slips were made from the same raw clays as the bodies, but with no or little added rock temper and/or with the sieving of the slip clay. Contextual analyses give further insights, including the possible uses of slips and washes for decoration and to decrease vessel wall permeability. Calcite and apatite coatings on the vessel surfaces also were observed and are interpreted. Results indicate greater continuity between and Midwestern and Southeastern United States in ceramic technology than previously thought, and suggest a need for caution in electron microprobe and INAA chemical studies of Midwestern ceramics.