The meaning-making practices of science are multimodal and include representational forms such as spoken and written language, diagrams, graphs, equations, and images. Science learning proceeds through an ever-increasing grasp of such resources. This study aims at providing insight into how a combination of Interaction Analysis (IA) and social semiotic analysis can provide a deeper understanding of students' engagement and learning with science representations. Social semiotics offers an analytical lens and categories for interpreting nuances of meaning in the visual domain. IA places a strong methodological emphasis on grounding analysis in unfolding interactions among peers, teachers, and artefacts. Investigating a teaching design where students iteratively produce multimodal drawings of the greenhouse effect, we used a multimodal analysis of the students' drawings and an IA of transcribed video recordings of students' interactions with each other and their teacher. The analyses show a progression towards more scientific student drawings over the course of a lesson. This progression was made possible by sustained attention to critical details in the drawings, and the drawings and interactions were instrumental in developing a more sophisticated understanding of the mechanisms behind the greenhouse effect. IA provides important analytical insights into students' interest in the situation, which is at the heart of social semiotics. Social semiotics offers insight into the nuances of students' interpretations of the world and how they relate to the practices of disciplinary science.