Documenting collaborative knowledge construction is critical for research in computer-supported collaborative learning. Because this is a multifaceted phenomenon, mixed methods are necessary to construct a good understanding of collaborative interactions, otherwise there is a risk of being overly reductionistic. In this paper I use quantitative methods of verbal data analysis, qualitative analysis, and techniques of data representation to characterize two successful knowledge building interactions from a sociocultural perspective. In the first study, a computer simulation helped mediate the interaction and in the second, a student-constructed representation was an important mediator. A fine-grained turn-by-turn analysis of the group discussions was supplemented with qualitative analysis of larger units of dialogue. In addition, chronological representations of discourse features and tool-related activity were used in study 2 to gain an integrated understanding of how a student-generated representation mediated collaborative knowledge construction. It is only by mixing methods that collaborative knowledge construction can be well characterized.