Etching isn’t caused by water spots alone—insect remains, bird droppings and acid rain can all etch your finish as well. So how exactly does an etch occur? We’re going to get into the science of it here, using the water spot as an example.
From mineral deposit to stain
When a water spot first dries on your finish, it leaves an accumulation of mineral content not unlike a coffee stain. These are pretty easy to remove since they aren’t bonded to the finish. But the longer the spot sits under the beating sun, the more UV rays react with the minerals in such a way that they bond to the finish. The stain’s bond can be broken down chemically, but mechanical removal through claying and buffing may also be necessary to fully remove the baked-on residue.
From stain to etch
Let’s say the water spot isn’t removed while in the stain stage, and UV radiation continues to hit the bonded minerals. What happens then? UV rays can cause a reaction in the minerals that raises the pH level, which is what determines how harsh a solution is. At a high or low enough pH level, a solution will literally eat through solids it comes in contact with, forming an indentation in the surface. That’s an etch mark. Low pH (aka acidic) solutions also chew through finishes—think insect remains, bird droppings, acid rain, even leaves from a tree.
Removing Water Spots
Fresh water spots
If you catch a water spot early, while it’s still just some residue on your finish, you’ll be able to wipe it up pretty easily with a quick detailer spray. Just make sure you’re using a soft, microfiber towel to minimize abrasion and therefore fine scratches.
Baked-on water spots
If a water spot isn’t removed early on, UV radiation will start baking the mineral residue into the finish. At this point, you’ll need something slightly more acidic than a quick detailer to break down the alkaline minerals. Something like an insect remover spray or tar remover. Use the same process as above, just again make sure you’re not rubbing too hard with the microfiber.
If that didn’t do the trick, you may want to amp up the acidity and instead use a 1:1 white vinegar/distilled water solution. Again, let the solution sit for a few minutes before you go to wipe down. And make sure you do a quick wash first to remove loose gunk so you’re not grinding it into the finish when you’re wiping.
Stained or etched water spots
Continued UV radiation will bake the mineral residue in even further, resulting in a smooth-feeling stain that doesn’t raise above the finish. Even more UV exposure will cause a chemical reaction that ups the stain’s alkalinity to the point it etches through the finish, forming a concave mark. When you’ve reached this level of water spot, it’ll be impossible to remove without mechanical decontamination and heavy abrasion.
Having a ceramic coating on top of your paint will buy you some time before this happens, but even highly chemically resistant coatings can still etch. To remove, you’ll need to take a clay bar to the water spot, then buff it out with a random orbital buffer. Just make sure you’re starting with the softest pad and least aggressive polish, then working your way up in terms of aggressiveness if you’re not seeing results. And if you’re not confident in your buffing abilities, you’ll want to get in touch with a reputable professional detailer to see if this work can be done for you.
Because stained or etched water spots require heavy abrasion to remove, it’s going to cost you a sliver of your already-thin clear coat. In the case of a clear coat failure, get a respray.
Stopping Water Spots
Static water beads can dry into water spots that can permanently stain and even etch through your finish. At that point, you’ll need some machine buffing to get them off, which often means you’re either shaving off precious clear coat or wearing down your ceramic coating to the point where you’ll need to re-apply. Not exactly a good position to be in. But there are ways how to prevent water spots on a car:
Get a coating that sheds beads
The simplest way to prevent a water spot is to get a coating that either sheds beads easily or sheets water outright. After all, if there are no beads on your finish, they won’t be able to leave a mark. To be fair, no coating will ever completely stop water from resting on your finish, but ones that repel water the best will prevent static beads, and therefore water spots, to the greatest possible extent.
Use distilled water when washing
Water spots are caused by mineral content inside the water beads left behind on your finish. So if you’re washing your car on a hot day with regular tap water, you’ll likely have water beads drying into water spots on your finish before you can dry them yourself. Either that, or you’ll inevitably miss a bead or two while drying and notice days later a stain has formed in some hard-to-reach area. Use distilled water devoid of mineral content, however, and all of this becomes a non-issue. No minerals, no residue.
Not everyone has easy access to distilled water, of course. In that case, you’ll want to make sure you’re drying your car post-wash as thoroughly as possible. Go over every nook and cranny on your finish and ensure no one bead is left behind.
Keep away from rain & sprinklers
Water is just about everywhere on this green Earth. So how are you supposed to go about avoiding it? Well, consider two of the most common sources of water spots: overnight rain and lawn sprinklers, hitting your car while it’s parked outside. Because these happen while you’re away from your car, there’s more time for the spot to stain or etch before you can remove it.
The obvious solution, therefore, is to have your car garaged or wrapped in a car cover when not in use. Beyond covers and garaging, paint protection film would also keep the car from being exposed to water when not in use, but it should be noted PPF can stain and etch.
ABC: Always Be Checking (for water spots)
It might sound exhausting, but if you’re serious about keeping a perfect finish, you need to be inspecting your vehicle for water spots (and other staining/etching contaminants, for that matter) as often as possible. The reasoning is simple; water spots need to be caught early on so they don’t get the chance to stain or etch. And like we just mentioned, keep a lookout for stuff like insect remains, road tar and sap, too, since they can all stain and in some case etch.
At the end of the day, water spots are an inevitability. But with the right ceramic coating, precautions, and vigilance, you’ll never run into one you can’t easily remove. Paint protection film is one of the best ways to keep your vehicle’s paint safe.