This investigation is focused on possible links between the development of critical attitude and conceptual understanding. We conducted a fine grained analysis of five student teachers' critical and conceptual development during a one hour and a half interaction with an expert. This investigation completes a series of three previous studies addressing the same general research question with different physics topics. In this instance, the focus is on the topic of osmosis. In line with an integrative perspective, the interviews provide some opportunities to link osmosis phenomena with a molecular approach. The transcripts were processed following two lines of analysis, one conceptual and the other focusing on critical attitude as well as metacognitive and affective affects. The findings suggest that students need to reach a threshold of comprehension, beyond logical necessity, before expressing critiques toward inaccurate texts. The prevalence of such "delayed critiques" aligns with our previous results. Additionally, a more specific finding of this study is the precise localization of events that are likely to trigger rapid conceptual and critical evolution. A discussion about further research and perspectives concerning the teaching of osmosis and students' formation to critique ends the paper.