Car wax: what it does, the three kinds, and how to put it on

Wax is a thin layer that sits on top of the clear coat and takes what the sun, the rain and the dust would otherwise do to the paint. It makes water bead and run off, makes the next wash easier, and gives the colour depth. It wears away doing that, which is why it has to go back on.

How long a coat lasts in this climate, and how to tell it has gone, is on how often to wax your car. Wax is also the last step of our interior and exterior detail, on paint that has been washed, decontaminated and polished first.

What a coat of wax actually does

Three things. It is a sacrificial layer: rain, dust, bird droppings and sun land on the wax and spend it instead of the clear coat. It changes how water behaves: on a waxed panel water pulls into beads and runs off, so less of it dries in place and leaves the mineral rings this market calls acid rain. And it fills the finest texture in the clear coat, which is where the depth and the gloss come from.

It does not harden the paint. A stone chip goes through wax as if it were not there, and so does a scratch from a dirty cloth. What wax changes is how much of the ordinary daily wear reaches the clear coat, and how easily the next wash comes off.

The three kinds

Carnauba wax: A natural wax from a Brazilian palm, sold as a paste or a liquid. It gives the warmest, deepest gloss of the three and lasts the shortest time. Practical Motoring puts pure carnauba at about every two months in Australian sun, with four months as pushing it. Here, with the same sun every month of the year, the shorter end is the honest one.
Synthetic sealant: A synthetic polymer that bonds to the clear coat and cures into something closer to a rigid shell. It protects for longest, up to a year on the same source in a cooler climate, and the look is flatter and glassier than carnauba. Poured, spread thin and buffed, the same as a wax.
Spray wax: A thin blend misted onto a clean panel and wiped off, in minutes. It tops up whatever is already there and makes drying easier. On its own it is not protection for a car that lives outdoors; it is what goes on between proper coats.

They are not either-or. A sealant underneath for the protection and a coat of carnauba over it for the look is a common pairing, with a spray wax after washes to keep both going. Shops here sell all three under the one word wax, so read the tin: a sealant says polymer or synthetic on it, a carnauba says carnauba, and a spray wax is the one in a trigger bottle.

Putting it on

On a car that has been washed and dried the same day. Wax over dust holds the dust against the paint, and wax over a greasy film does not bond at all.
On a cool panel in the shade. A hot panel bakes the wax on in patches that will not buff off cleanly.
Thin. A coat you can barely see goes on evenly and comes off cleanly; a thick one wastes most of the tin and streaks. Use the applicator pad, one panel at a time.
Let it haze, then buff with a clean microfibre, turning the cloth as it loads. Check the panel from a low angle against the light for streaks.
Keep it off unpainted black plastic and rubber, where it dries white and is hard to get out of the grain.
If the paint feels rough under the back of your hand, it is contaminated, and waxing traps that in. The surface needs decontaminating first, which is part of a detail rather than something a tin and a cloth can do.

The wash that comes before the wax matters as much as the wax. The order is on how to wash a car, and the mistakes that put scratches under a new coat are on DIY car wash tips.

How long it lasts here

Shorter than the tin says. The tin was written for somewhere with a winter, and a car here gets the same overhead sun in January as in June. Heat softens a carnauba coat, rain spends it, and a strong detergent strips it in one wash. The interval by where the car is parked, the water test that tells you the coat is going, and the three things wax will not do are all on how often to wax your car.

If a scratch or a patch of dullness is already in the paint, wax will sit over it and change nothing underneath. Which marks polish out before the wax goes on is on what is on your paint.

Wax is the last step of the detail

In the exterior half of our interior and exterior detail the wash comes first, then the polish works on what the wash leaves behind, and the wax goes on last to sit between the paint and the sun. It is done at your address, with the car where it is parked. Say in the form when the car was last waxed, if you know, and what the water does on the hood after rain.

Book a detail Or text the crew

Sources

Practical Motoring, myth busting: carnauba wax versus synthetic. Carnauba reapplied about every two months depending on climate, a sealant as a rigid shell lasting up to twelve months, and carnauba over a sealant for depth. practicalmotoring.com.au
Chemical Guys, does car wax actually protect your paint: a water-repelling, UV-blocking layer that degrades with washing, friction and sun, and does not stop scratches or chips. chemicalguys.com