The interpretation of craft activity in Mesoamerica has been hindered by difficulties in recognizing and defining the archaeological signatures associated with obsidian blade production and consumption. Theoretical advances and experimental approaches have improved our understanding, but few studies have investigated the role of obsidian blade production in craft activity using empirical data from archaeological assemblages. The present study addresses this problem by presenting an analysis of obsidian flakes and blades recovered from a workshop refuse context at Kaminaljuyu, Guatemala. Technological and use wear analyses suggest that core-shaping by-products in the form of irregular percussion and pressure blades were used in craft activity. Fine blades were underrepresented in the assemblage, suggesting that cores or blades left the workshop as finished goods. These analyses demonstrate that the actual behavior of artisans likely did not conform exactly to the dichotomous theoretical categories of production and consumption that archaeologists routinely use.