Why your black car looks worse after a wash
Swirl marks are not put in by the road. They are put in by mitts, sponges and drying towels, and by the brush wash at the end of the street. Here is what actually causes them, and the four changes that stop it.
Written by Tom Hartley, who has corrected more of them than he would like to count.
The road is not the problem
Ask anyone with a black car where the swirls came from and they will tell you the same thing: the roads, the motorway, the car park. It sounds right. It is almost never true.
Swirl marks are shallow, circular scratches in the clear lacquer. They are made by something dragging grit across the paint in a circle, at close quarters, under light pressure. Road grime does not do that. A mitt, a sponge, a drying towel and a brush wash all do exactly that, several times a month, for years.
Why they only appear afterwards
A dirty car hides its own damage. Dust and road film scatter light before it reaches the lacquer, so reflections are soft and the surface looks flat and even. Wash the car and you remove that layer, and now the light goes straight in and comes back out through every one of those grooves.
That is why the car can look worse in the driveway on a sunny Sunday than it did filthy on the Friday. Nothing new happened to it. You just took the veil off.
The four things that actually cause it
The brush wash. Rotating brushes carry the grit from the last hundred cars. One pass puts in more marring than a year of driving.
One bucket. Every time the mitt goes back into dirty water it picks the grit back up and carries it to the next panel. Two buckets with grit guards, one for shampoo and one to rinse the mitt, removes most of the problem for the price of a bucket.
The wrong mitt. Sponges and old cloths trap grit on the surface and drag it. A deep-pile microfibre mitt lets grit fall away from the paint into the pile.
Drying badly. Rubbing a car dry with a hard towel in circles is the classic. A large, plush drying towel laid flat and drawn in straight lines, or a blower, avoids it entirely.
How deep is a swirl, really
This is where it gets useful. Your clear coat is roughly 35 to 50 microns thick. A typical swirl is one to three microns deep. That is why polishing works: levelling a couple of microns of lacquer removes the groove and leaves the great majority of the clear coat intact.
It is also why polishing is not a free move. Every correction takes some of the layer that carries your paint's UV protection and gloss. A car that gets corrected every year because it keeps getting swirled will run out of lacquer long before its owner runs out of enthusiasm.
What we do about it
Correction removes what is there. That is a day or three at the unit, depending on the paint, and it is measured before and after, so you know exactly what was taken.
A coating makes the car easier to wash, which is the part that keeps the swirls away. Dirt releases with less agitation, so the mitt does less work and puts in fewer marks.
The maintenance round is the boring answer that works. A safe wash, the same way, every fortnight or month, and the paint simply stays right. Cars on our round almost never need correcting twice.
If you do nothing else
Stop using brush washes. Buy a second bucket, a grit guard, a decent mitt and a big drying towel. That is about forty pounds and it will do more for your paint than any product on a shelf.
And if the car is already swirled, do not let anyone quote you for correction without measuring the paint first. If they are not putting a gauge on it, they are guessing with your lacquer.
