Paint scratches, swirl marks and what polishing removes

What do detailing-product makers say about scratches, swirl marks and oxidation?

Turtle Wax, a car-care product maker, groups surface scratches, swirl marks and oxidation together as the defects its paint correction tools are used to remove. Jimbo's Detailing, another detailing-product maker, says swirls and scratches scatter light unevenly, which makes paint look dull.

On a page about paint protection, Jimbo's lists ultraviolet radiation as something that breaks down clear coat over time, causes oxidation and reduces gloss clarity.

How is clear coat built, and how can scratch depth be checked?

Jimbo's says most modern cars have a clear coat 30 to 50 microns thick, which it compares to about half the thickness of a human hair. It lists a primer layer of roughly 10 to 20 microns and a base color layer of roughly 10 to 20 microns, and calls the clear coat the thickest of the three layers. It also says swirls and light scratches affect only the uppermost microns of clear coat.

Chemical Guys, a detailing-product maker, says most scratches fall into one of two camps: they sit in the clear coat, or they cut through it into the color coat or the metal underneath. Its simple owner check is to drag a fingernail gently across the mark. If the nail glides over without catching, it says you are likely looking at a surface-level scratch; if it catches or snags, the damage goes deeper. Chemical Guys suggests washing and drying the panel first so dirt or old wax does not skew the read.

What does polishing remove, and how does it relate to paint correction?

Turtle Wax says most car polishes contain polishing agents, tiny abrasives that help remove scratches and swirls from the clear coat. It describes them as buffing away an extremely thin layer of damaged clear coat to reveal a fresh, transparent surface underneath.

Jimbo's gives estimates by type: about 1 to 2 microns of clear coat for a light polish, 2 to 4 for a medium polish and 4 to 5 or more for a heavy compound. It also says compounds cut deeper and remove more clear coat than polish does.

Jimbo's says polishing is one part of paint correction, which it describes as the full process of defect removal and which may include compounding, polishing and finishing.

What happens after polishing, and can paint be polished too often?

Jimbo's says polishing removes a thin layer of clear coat, and that this leaves paint vulnerable until it is protected; it recommends a ceramic spray or coating after polishing.

Jimbo's also says over-polishing can thin the clear coat to the point where it no longer protects the base coat, with patchy gloss and exposed color coat among the signs, and that frequent polishing removes clear coat unnecessarily. If a car has been heavily polished several times, Jimbo's says to assume it has less clear coat left.