The paper is dedicated to one of the stages in the history of studying glazed ceramics from the medieval Kazan Kremlin and Kazan. The main results of the archaeological studies of 1923–1956 conducted by N.F. Kalinin in the territory of the Kazan Kremlin and the suburban part of the city are demonstrated by the author. The works by Kalinin feature the first attempts to classify and systematize non-glazed ceramics. He was the first to use technological attributes in the systematization of ceramics: texture, shard color, thickness and density, using these parameters to classify all Bolgar-Tatar ceramics into six groups, and Russian ceramics - into 4 groups. N.F. Kalinin also distinguished molded ceramics. The results obtained during the study of non-glazed ceramics are important not only for studying the history of Kazan, but also for the history of the region in general.