Next to maybe swirl marks, water spots are probably the most annoying thing to deal with when detailing. They can run a range of severity and require various approaches to remove depending on where they are on the vehicle.
The goal of this writeup is to help you better understand water spots and more importantly how to remove them.
WHAT ARE WATER SPOTS?
Simply put, a water spot is the stuff that was suspended in the droplet before the water dried/evaporated. Depending on the source of the water and where it had been before drying you can see any number of things cause the actual spot.
Ground water is the most common culprit. The water from a mis-aimed sprinkler or the water used from your hose is full of minerals. The type of mineral and concentration varies from region to region and based on how 'hard' your water is you may see more severe spotting. Rain water typically carries a different type of contamination. As that little droplet fell thru the air it picked up airborne pollution as well as dust or dirt, plus if the water ran off of a tree or nearby roof before landing on your car it took some of the contamination from those surfaces as well. Road water would be the very dirty water that is splashed up behind your wheels or all over the lower regions of your car when driving in wet conditions. Its almost impossible to know what is suspended in that water, but for sure it contains all manner of very nasty dirt, chemicals, and other road grime.
WHAT IS BONDED MINERAL CONTAMINATION?
Bonded minerals are just a more severe form of water spot. When mineral concentrations are higher, or a car is subjected to lots of ground water drying on the surface (sprinklers hit a car every morning) water spots can become bonded minerals. These are a little more difficult to deal with as they form hard bonds with the clear coat that make them harder to remove. Once removed bonded mineral contamination can sometimes leave the area where it was looking dull or even pitted.
WHAT IS ETCHING?
Etching is the worst case scenario in the progression of water spots. Etching is typically seen from water thats baked on in direct sunlight or high heat. It is also prevalent with acid rain or ground water with high levels of chlorine. Etching can be minor to severe, with the most severe kind requiring very aggressive means of correction - potentially wet sanding in extreme cases. Etching is a circumstance where the water spot has physically 'eaten' its way into the clear coat so that it sits at a lower level than the surrounding surface.
These processes are listed in order from least to most aggressive.
WHAT ABOUT ON GLASS?
The exact same rules apply for glass, but with one exception - glass is far harder than clear coat so it allows for more aggressive options when finer options fail. After attempting the above steps on glass, if you have not seen improvement or complete removal there is 1 more step to attempt.
As with anything prevention is the best medicine.