For classical nucleation theory predictions, I will need the interfacial tension with water, molar volume, and saturation concentration of sulfur. To obtain values at room temperature, it is necessary (and common practice) to extrapolate the density and interfacial tension. The density of the sulfur hydrosol is estimated as 1.90±0.03 g/mL (using inaccuracy of 1.5%). The interfacial tension is estimated as 67.7±0.2 dynes/cm (where the error is obtained by reproducing the fit -see S1). The solubility of elemental sulfur in water is reported as 1.9±0.6 mol S 8 /kg. Besides these properties, I need the concentration of sulfur dissolved in solution at the peak of supersaturation.