A simulation of laboratory experiments on the condensation of individual chemicals and water on soot aggregates was performed using a two-step approach. In the first step (Supplementary Information section 5), the condensation of a pure chemical was considered using a kinetic model that accounted for the convex surface of primary spheres and concave surface of meniscus in junctions between the spheres. The vapor pressure of the condensate is elevated above the convex surface and depressed above the concave surface due to the Kelvin effect associated with the positive and negative curvature, respectively. Due to the depressed saturation pressure above concave surfaces, condensation can occur even in subsaturated vapor (𝑆 < 1), 𝑆 = 𝑝 gas 𝑝 sat,p