the known and frequency-independent calculated concentration was used to calculate the equivalent absorption if it was fully liquid (α liquid ). Of the three frequencies described here, the data at 0.5 THz were the least affected by the crystalline feature, since that frequency was the furthest away from the feature at 1.6 THz. Therefore, the concentration calculated from it was being used as the basis to calculate α liquid . The relative difference compared to the measured absorption is plotted in Figure for different experimental stages. Before crystals were observed in the field of view, the relative difference was close to zero for all frequencies. During crystal growth into the field of view however, the relative difference increased between 1.5 THz to 1.7 THz, and decreased between 0.6 THz to 1.4 THz. This effect became even stronger once crystallisation was complete.