Evaporation of pointy ice drops: smoothing out the singularity

Although not as commonly observed as the evaporation of liquid water, ice does evaporate (or sublimate) below 0°C provided the surrounding air is sufficiently dry, i.e. with a relative humidity over ice below 100%. Through controlled experiments, we study the evaporation of sessile ice drops crowned with a conical tip: pointy ice drops. We show that, like liquid droplets, their evaporation is diffusion limited and strongly enhanced at sharp points: their edges and tip. However, unlike liquid droplets whose sharp edges are maintained by surface tension, the tip and edges of our pointy ice drop, originally sharp are quickly smoothed out. We accurately predict the whole drop evaporation using finite element simulations and present simple analytical results for the tip smoothing at short time and the evaporation of the latter smoothen ice drop. Our results being also applicable to diffusion limited dissolution, we expect them to be relevant in pharmaceutical applications.