I like my car a lot. But I have to admit, it doesn’t look as good as it used to. And probably yours doesn’t either. That’s because the moment your car rolls out the factory door, its finish starts to deteriorate.
It’s not too surprising, since a car’s surface is attacked by ultraviolet light, ozone, heat, acid rain, industrial fallout, squashed insects, bird droppings, tree sap, road salt, and even hard water.
Of course, as I mentioned last week, the first step in fending off the damage from all these things is painting the car, but you want more than just color: you want a shiny, reflective coating that will last for years.
To get that, you have to put something over the paint, because although the paint by itself would last for years, it wouldn’t look good for very long. Paint exposed to the air immediately begins to combine with oxygen. It becomes dull. In extreme cases, the pigment will actually rub off on your hand.
And all those other things I mentioned at the top of the column have equally devastating effects on bare paint. Even if acid rain isn’t a problem where you live, but you can get the same effect in any city when industrial fallout containing sulfur dioxide and nitrogen oxide settle on your car in a dry form. Dew, raindrops or water from a sprinkler can mix with these chemicals to form a weak dilution of sulfuric acid. As the moisture evaporates, that acid becomes more and more concentrated, and begins to eat into the paint surface. Even a bird dropping (like the big ugly splotch I noticed on my hood this morning) can etch into the paint if it’s left too long, especially on hot days..
Paint is protected from these things in one of two days: with wax, or with the increasingly popular “clear-coat.”
The protection wax offers is seen best when it rains: whereas water will spread out into a thin film over an unwaxed car, on a freshly waxed car the water beads. That’s because water molecules are less attracted to the waxy surface than they are to other water molecules, so they pull themselves together into clumps. Without the wax, the molecules are more attracted to the surface than to themselves, and so they spread out–and do more damage.
The best wax for an automobile is carnauba wax, which is beaten from the leaves of the carnauba palm, cultivated in Brazil. It’s very hard and has a high melting point, which makes it ideal for automotive finishes (you want it hard to offer more protection; you want it to have a high melting point so it doesn’t melt off your car on hot days). Cars protected only with wax require re-waxing at least twice a year, sometimes more.
A clear-coated car, on the other hand, has a more permanent protective layer: a thin film of acrylic resin. Owners of clear-coated cars are sometimes told they shouldn’t wax at all, but although the clear-coat does ensure that the finish remains shiny, the surface can still be dulled by pollution and grime, so an occasional waxing, say once a year, is still helpful.
The compounds used in waxing either kind of car usually contain more than just wax. For a conventionally finished car, combination cleaner/waxes are best. They contain abrasives that strip away the residue of oxidized paint, exposing a fresh layer of paint, which, when waxed, will look like new. That’s exactly the wrong kind of wax to use on a clear-coated car, though: the abrasives will scratch the clear-coat.
Some of the latest products to appear are polishes color-matched to your car’s paint. The color is deposited into scratches, nicks and other imperfections in the clear-coat.
A slightly different approach is taken by products actually change the way the clearcoat reflects light. For light-colored cars, there’s a formula that makes the clear-coat reflect light better, making the finish brighter. For dark-colored cars, there’s a product that helps the clear-coat absorb light, making the finish look darker and glossier.
But only a few car-owners will go to such extremes. For most of us, the best advice for taking care of a car’s finish is to wash it when it’s dirty and wax it once or twice a year.
Considering what my car looks like at the moment, it’s obviously time I took my own advice.