Mineral deposits are spots of minerals that are left behind after the carrier has evaporated. Although the liquid evaporates, the minerals in that liquid don’t. They are left behind.
The minerals in water
Minerals are naturally occurring substances. Of all the liquids a detailer/valeter uses, water is the most used one. Water is rarely just a pure form of H2O (hydrogen and oxygen). More often it contains several trace elements and minerals. When looking at the quality of water, certain variables that are taken into account are:
- Color of water
- Taste and odor (geosmin, 2-Methylisoborneol (MIB), etc.)
- Dissolved metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium)
- Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia lamblia; see Bacteriological water analysis
- Dissolved metals and metalloids (lead, mercury, arsenic, etc.)
- Dissolved organics: colored dissolved organic matter (CDOM), dissolved organic carbon (DOC)
- Heavy metals
- Hormone analogs
How evaporation comes into play
When water evaporates (it doesn’t have to boil to evaporate) it leaves behind many if not all of these substances. Evaporation is a different process to boiling. The first is a surface effect that happens at any time, while the latter is a bulk transformation that only happens when the conditions are correct. Technically the water is not turning into a gas, but random movement of the surface molecules allows some of them enough energy to escape from the surface into the air. The rate at which they leave the surface depends on a number of factors – for instance the temperature of both air and water, the humidity of the air, and the size of the surface exposed. When the bridge is ‘steaming’: the wood is marginally warmer than the air (due to the sun shine), the air is very humid (it has just been raining) and the water is spread out to expose a very large surface area. In fact, since the air is cooler and almost saturated with water, the molecules of water are almost immediately condensing into micro-droplets in the air – which is why you can see them.
how they end up on your vehicle
After the water has evaporated, certain substances are being left behind. These substances form a small layer. When a droplet forms on a car, the round shape helps the sunlight to be directed just like a magnifying glass. Heating up the surface underneath and warming up the droplet even more. The faster the droplet evaporates, the more substances are left behind. The combination of directed sunlight with the amount of substances in the water droplet, can actually cause a slight etching effect, which can later be seen as very small ‘drop-like’ imperfections in the surface that can only be polished out. In very extreme cases, these imperfection can’t be polished out and might need a respray.
The shape of the bead makes it fairly big in volume with a relative small surface. This causes the droplet to evaporate less quickly then a flat puddle of water. It is very common to still see drops of water on a car with great beading, even though the unprotected car next to it is already completely dry. Ironically, waterspots can be lessened by preventing nice, full, round beads. The greater the complete wetting-effect, the smaller the risk of mineral deposits and the quicker the water will ‘dry up’.
Decreasing the risk of mineral deposits
It is not to difficult to have more control over mineral deposits.
- Rain water contains very few hard minerals and will be much less likely to leave any mineral deposits
- Tapwater is generally much heavier in minerals, which is good for your body, but not for the car
- You can use a water filter that helps to filter out as many particles as possible
- You could use distilled water, which will contain very few contaminants. This can also be called; osmose water, purified water, filtered water, demineralised water
How to remove them
In most cases just washing the car regularly will remove the largest of them. In some more rare cases you can use the claying-process to remove them safely. The effect they have on the paintwork might need polishing to remove. In very extreme cases it might need a respray or spot repair.
Product most prone to waterspots products
In general, most products aren’t affected very much by waterspots. However, ceramic coatings have a tendency to be much more prone to waterspots because of their chemical make-up. This can sometimes be prevented by applying a spray sealant which is based on the same ingredients, polymers or overall technology.