  It has been conjectured that roughness plays a role in surface nucleation,
the tendency for freezing to begin preferentially at the liquid-gas interface.
Using high speed imaging, we sought evidence for freezing at the contact line
on catalyst substrates with imposed characteristic length scales (texture).
Length scales consistent with the critical nucleus size and with $\delta \sim
\tau / \sigma$, where $\tau$ is a relevant line tension and $\sigma$ is the
surface tension, range from nanometers to micron. It is found that nano-scale
texture causes a shift in the nucleation of ice in supercooled water to the
three-phase contact line, while micro-scale texture does not.
