Large defects of very low concentration and internal stresses are believed to control various properties of ceramics. To obtain good ceramics, it is crucial to remove these defects from the otherwise homogeneous microstructure. This paper defines a method to show the characteristics and origins of defects and other structural features that are detrimental to the properties. The novel characterization technique applied in this study is the liquid immersion method. In this method, specimens in various stages of processing are made transparent with an immersion liquid and subsequently examined with a normal optical and/or polarized light microscope in the transmission mode. The detrimental features include large pores, large particles, large aggregates and particle orientation. Means are suggested to minimize these detrimental features.