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Anatomy of a Water Spot: Understanding and Preventing Paint Damage

Updated: Oct 10, 2023

Any car enthusiast will tell you that a clean, shiny vehicle is a joy to behold. Few things catch the attention of car lovers faster than a vehicle that looks good glistening in the sun. But, a good paint job isn't just aesthetically pleasing – it is also protective and preserves the longevity of the bodywork. However, one common (and ugly) issue that car owners frequently face is water spots! Maybe it was the recent rainstorm that deposited water on the paint that then dried. Perhaps it was an errant sprinkler that sprayed the car. A rogue puddle splashed dirty road water up. Regardless of the reason, water spots are an unsightly artifact that immediately detracts from that beautiful automotive exterior. They come in many shapes, sizes, and types with varying levels of risk, but understanding the anatomy of these spots and how to prevent them is vital for keeping your vehicle looking its best.



First, what Are Water Spots?

We certainly all know a water spot when we see one, but what are they technically? Water spots are marks left on a car's paintwork after the water has evaporated off the surface. The contents of the water that was on the surface, combined with what other contamination it may have already been on the car where the water landed dictate the characteristics of the water spot. The residues left behind are commonly a mixture of minerals like calcium or magnesium but can also contain industrial pollutants and organic material like pollen. The severity of the spots can vary wildly as can the effort required to remove them, particularly if left untreated for long periods. Water spots are typically categorized into three types:

1. Type I - Mineral Deposit Spots: These spots occur when water evaporates off the vehicle, leaving behind minerals on the surface. These spots are a surface-level issue that can be relatively easy to remove. If your vehicle is well maintained and the mineral deposit is not left to dwell on the surface for too long, they will usually disappear with nothing more than a wash. If you encounter a mineral deposit that is slightly more stubborn than a wash can handle, a quick detailer or spray wax can help.

2. Type II - Bonded Mineral Spots: These are a bit more serious than Type I spots. They occur when mineral deposits have bonded to the paintwork's surface, typically because the mineral content of the water was very high, or the spots were left unaddressed for a long period of time. Type II spots may require more intensive cleaning products or techniques for removal. A dedicated water spot remover, or a mixture of white vinegar mixed 2:1 with distilled water is an effective way to deal with most bonded mineral spots. In some cases, a mechanical decontamination method like a clay bar may be required depending on the severity of the spots.

3. Type III - Erosion Spots or Etching: These are the most severe type of water spots, and in reality, aren’t water spots at all, but more of a physical defect in the paint caused by neglected water spots. Erosion spots occur when the minerals in the water have started to physically eat away at the vehicle's clear coat because the contamination was so high in mineral content that it was corrosive. These types of spots are most common from groundwater, like spray from irrigation sprinklers, and are typically made worse by heat and UV rays speeding up the evaporation process. They will typically appear more as a ring shape than a single spot. In general, erosions spots or etching cannot be removed with topical solutions alone and will require specialized processes including heavy compounding and/or wet sanding to fully correct.




Spot-Free Water Eliminates The Source of Spots One surefire way to prevent water spots is to make sure the water that meets your vehicle is spot-free. Easier said than done right? You don’t have control over rainwater, puddles along the road, or what comes out of your neighbor’s sprinklers that were accidentally aimed at your car instead of the grass. Where you can control it is how you choose to wash. Many inferior car washes use a combination of unfiltered tap water and reclaimed wash water that is loaded with contamination. Filtering this water is expensive and complicated so many washes simply choose to skip filtration. At Autowash we know you love your car, and you care about keeping it looking its best, which is why we use a multi-stage filtration process with our water that filters out 99.9999995% of minerals and contamination. Spot-free rinse is a standard part of all the touch-free automatic washes at Autowash and is available as a rinse cycle in our self-serve bays. Because the water is free of nearly all contamination, even if it does dry on your vehicle it will easily be removed, or in most cases leave no evidence behind at all! Chemical Reactions

The type of soap used at a car wash is also important. High-quality car wash soaps are formulated to be non-corrosive, preventing any harsh reactions with your car's paint or clear coat. Lower-quality car washes like cutting corners by using chemistry that is highly corrosive to “burn” the dirt from your finish. Not only is this bad for your car in general, but these acids can also react with the deposits in water spots and make the spots worse! Effectively these chemical reactions can take your Type I or Type II spot we described earlier and make it a Type III. Again, here Autowash goes further to make sure our customers get the best wash possible for their car, using only the highest quality acid-free soaps to neutralize contamination and avoid making things worse with unwanted or unexpected chemical reactions.


Avoiding Spotty Problems

As we mentioned earlier, it is virtually impossible to control all the factors that contribute to water spots, but there are some things you can do to make them less likely and easily removed should they happen. Prevention is the best medicine. While you can’t prevent all sources, you can avoid many of them.


  1. Maintain a protective barrier, whether it is traditional carnauba car wax, a sealant, or even a ceramic coating. Keeping a sacrificial barrier between the water and your paint can be the difference between easily-removed spots and stubborn Type III erosion.

  2. The longer they sit, the worse they get. Try to address water spots as soon as possible by either visiting the car wash or wiping them away with a quick detail spray and a microfiber towel.

  3. Avoid parking your car anywhere it could be sprayed by sprinklers. Groundwater is high in minerals and will certainly cause more severe water spots.

  4. Use spot-free water whenever possible. Choose a car wash, like Autowash, that invests in its filtration to provide spot-free water or add a filtration system to your home wash routine. Regardless of where or how you wash, eliminating the minerals and chemicals before it touches your car can prevent nearly all water spots.

  5. Clean cars are less likely to spot. As mentioned, it isn’t just what’s in the water when it lands, it is what it mixes with on your car. Pollen, dust, and fallout contribute to more stubborn spots. Keeping your vehicle clean will help reduce the severity of water spots.


Final Thoughts

Understanding the anatomy of a water spot and how it forms is the first step in preventing them. By taking a few simple steps to avoid water spots, then addressing them quickly and properly when they do happen you can preserve your vehicle's exterior appearance for years to come. After all, your vehicle is more than just a mode of transportation. It's an investment, and looking after the paintwork contributes significantly to maintaining its value and appeal.

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