Time evolution of the average agglomerate size for three different particle charges, collapsed onto each other to reveal the universal exponential convergence. The average sizes, ⟨M⟩(t), and average asymptotic sizes, ⟨M⟩_∞, are measured in numbers of primary particles. Both the average asymptotic sizes and the characteristic times, t*, are used as fit parameters; refer to Table 2 for their values. The dashed line is included to guide the eye.