In science education research, there is a growing body of studies focusing on the role of multiple representations in pupils' learning. This study is based on a social semiotic perspective and in the analysis, there is a special focus on how the content is conveyed and how relations are created through interaction between teachers/pupils and the infrared camera and between teachers and pupils. We report the results from a pilot study involving one teacher's work with thermal phenomena in grade 6. A class of 45 primary pupils, divided in 4 groups. Overall, we describe findings from three lessons involving experiments situated in pupils' everyday experiences of thermal phenomena. In the analysis, we focus on two groups of pupils (N = 25) and data are generated from three lessons by video and audio recordings. With the help of the infrared camera, the pupils manage to represent heat as a process. The infrared camera provides a visual interface for a shared point of reference and is an important semiotic resource for stimulating verbal communication between pupils and between pupils and teachers.