Why does the sodium become transparent after burning?

I know that if we throw a piece of sodium into water then it will melt first then it will explode.


But under different conditions, the above situation will not happen. If we keep a piece of sodium on a wet cloth then it will not explode. Rather, it will burn and turn into a transparent small ball and then the ball will bust. ([Video of example](https://www.youtube.com/watch?v=DJGVZNth68k).)


What is the reason behind such situation? What reaction actually occurs when the sodium is kept on wet cloth?


