Growth of Breath Figures

Abstract

Measurements are reported of the growth of breath figures, the patterns that form when a vapor is condensed onto a cold surface. The pattern for water on glass was studied by direct observation and light scattering as a function of the contact angle $\theta$, flux $F$, degree of supersaturation $\Delta T$, and time $t$. When $\theta =0\mathrm{}°$, a uniform layer forms whose thickness grows as $t$ at constant $F$ and $\Delta T$. For $\theta =90\mathrm{}°$ droplets are formed; at constant $F$ and $\Delta T$ the radius of an isolated droplet grows as $t^{0.23}$, but as a result of coalescences the average droplet radius grows as $t^{0.75}$. The growth process is self-similar—coalescences simply rescale the distances and leave the basic droplet pattern unaltered.