Jim
A similar thing happens when I clean my van and it's always baffled me, every time I wash it, water beads up on the paintwork !
I've actually done some research on the interweb and found out there are 1000's of small people, to small for us to see with our eyes and while I'm not entirely sure what it is they do and how they do it the scientific name given to them is 'little beaders'
Hope this answers your question mate
Paul