A range of examples are used to show how determining the composition of the reactive clay matrix of pottery can enhance our understanding of its sintering and vitrification behavior. Analysis of the glassy phase may allow the application of melt thermometers originally derived for igneous liquids. The compositions of glazes and slips can be determined without interference from the fabric. Aplastic mineral inclusions may have compositions reflecting the environment of formation and so may assist provenancing. Analysis of inclusions does not tend to be amenable to bulk chemical analysis techniques.