In Fig. , the parameter B, in general, is proportional to a specific surface of the solid phases when D > 3 (i.e. surface fractals, SI: Eq. S3). Initially, as gypsum crystals grow before ~4000 s (T = 35 °C), this parameter gradually decreases in both directions due to a reduction in surface-to-volume ratio. The decrease in surface-to-volume ratio suggests the development of larger crystals while smaller particles/crystals disappear, possibly through processes such as