I washed the car yesterday you know a quick rub down with an oily rag then a quick dry with a jammy leather.
So what has it done today yes you guessed it peed down with rain.
It has stopped now and brightened up so I decided to dry the car again as if it drys on its own it gets all nasty spots showing on the black paintwork.
Well when I wash it I only have to go over it once with the jammy leather and it is dry, but today I had to go over it 4 times before it would dry.
Howzat work den? and it was not because the jammy leather was wet from drying the car yesterday as I always keep it wet anyway.
if you have rubbed your car down with an oily rag or some other waxy substance, then some of it will still be there days after, thus when you try to get rain off with your shammy it will pick up some of that oil or wax, making it less absorbent.
....nah, I'm a naughtyboy not logic, the water you washed your car would've been pretty pure and a lot of your rinse water would just run off whereas rain water has micro particles of dust which make the droplets adhere to the paintwork so take longer to " jammy " off.......like it?
......ok then I will, tell me where you live and I'll be round with two buckets of water one filled from a tap and the other from a muddy puddle and lets see which one leaves the largest water droplets on ya car, add any particles to water and it will increase the viscosity..... take more water with it before getting abusive......
its because rian water is 4 times wetter than treated water which you get from the tap due mainly but not entirely to the fact that rain water contains more hydrogen particles