Relationship between H₂O (a), CH₃OH (b) ice column densities (N) and visual extinction (A_V) for lines of sights in nearby star-forming clusters: Corona Australis Coronet (triangles), Serpens SVS 4 (squares), and Orion B35A (circles). Upper limits are marked as arrows. The grey lines represent linear fits to the detections. We note that the visual extinction values obtained for CrA have to be taken with care as their determination is hampered by the lack of background stars towards the densest region of the Coronet cluster (see Sect. 4.2). The data for Serpens SVS 4 and Orion B35A were taken from Perotti et al. (2020, 2021), respectively.