Modeling of capillary condensation of vapors of individual chemicals and water. We used our recently developed capillary condensation model to predict the volume of condensate gained by fractal soot particles, as they traveled through the saturator. Fig. shows the increase in volume, expressed as the filling angle 𝜃 1 (see Fig. for reference), for different chemicals. The zero time corresponds to the saturator entrance and the 10° initial filling angle is due to the carbon neck between primary spheres (Supplementary information, section 5). After entering the saturator, the aerosol flow became gradually saturated by the evaporating and diffusing chemical, reaching a vapor saturation 𝜈 = 0.9 at the saturator exit. Despite identical vapor saturation for all chemicals, the model predicted vastly different condensate filling angles after a 25 s exposure: 48 for TDA, 45 for TEG and TEGMBE, 16 for GA, 14 for AN, and 11 for SA. One factor causing this spread was different wetting of the soot particle surface by different condensates. The second factor was related to the difference between vapor pressure above bulk material loaded in the saturator and vapor pressure above the condensate on particles. The latter was controlled by either the phase state or concentration of the chemical in the condensate, producing significantly different vapor saturations relative to particle phase, 𝑆 (equation 4 in Methods, Supplementary sections 2 and 6). Despite the different saturation ratios, the filling angle of condensate reached a steady state value for all chemicals except for SA, corresponding to an equilibrium between the meniscus and surrounding vapor. The equilibrium was never achieved for SA because its vapor was highly supersaturated relative to particles (𝑆 = 11.9) due to a significant stabilization of the SA condensate by hydration even at the residual 5% RH (Supplementary section 6). The high supersaturation of SA vapor produced an exponential increase in the filling angle with exposure time, but the total amount of condensate gained by the particles upon exiting the reservoir was limited by the low SA saturation vapor pressure. Overall, mass fractions of condensed chemicals predicted by our model were 0.1-3.7%, ranging from well below (SA) to slightly above (TDA) experimentally detectable mass gain. Such small amounts, when placed in the junctions, created sufficiently strong capillary forces to initiate small but measurable restructuring of the soot aggregates. Indeed, comparing 𝜃 1 at the saturator exit predicted by the model (Fig. ) against the extent of restructuring at the lowest humidity measured in the experiments (Fig. ) shows a clear trend, where a higher 𝜃 1 corresponds to a more significant decrease in the particle growth factor by diameter, Gfd. This observation is in agreement with previous studies performed using significantly larger amounts of single-component condensates. In the following, we describe the increase in the filling angle by capillary condensation of water when these hydrophilic soot aggregates were exposed to progressively higher RH.