This work deals with the technological aspects of medieval glass production. Results from archaeological excavations, insights from the analysis of written sources, and outcomes from archaeochemical experiments are combined to achieve a better understanding of the empirical knowledge of medieval glassmakers. It is particularly interesting to explore the connections that point to early history and classical times. Early modern illustrations of glassmaker furnaces still pose many puzzles, which can sometimes be surprisingly explained through comparisons. Additionally, new conclusions can be drawn from the connections identified. Archaeochemical investigations lead to an understanding of some unclear details that emerge during excavations or through careful study of written sources.