Calculating Angle for Water Rolling on Glass Plane

[Winzer]

Homework Statement

So I need to get a rough calculation:
At what angle does drops of water start rolling down a plane of glalss.
This is for my project where we are using a solar still to purify water. I just need ot get a rough calculation so I know at what angle to tilt the plane of glass. I am aware that I could experiment but for the class I need calculations.
Thanks.

 

[mgb_phys]

Surface tension is what is stopping the drops from moving.
You will need to investigate what parameters effect the surface tension - this is going to be dominated by the nature of the glass surfacd, how smooth, what type of glass (surface charge) and any impurities on the surface ( particulalry detergents).

There isn't a single number for just glass.