Boiling water droplet behavior impinging on heated liquid metal surface

We observed boiling behavior of a water drop impinging on a heated liquid metal surface. By using liquid metal as impinged surface, we are able to observe boiling behavior of a water drop impinging on perfectly smooth surface. As a result of experiment, we found that a water drop starts boiling with the time delay after impinging and it changes by Weber number and initial surface temperature. And we also found that there are three factors which induce the direct contact of a water drop and surface by shooting in a high frame rate.