Last month Jason Killmer showed us how to make a nearly shiny surface dull. As counterproductive as it seems, sanding a somewhat shiny finish is the first step to achieve a potentially shinier one.
As he explained in that tutorial, color sanding is merely an extension of the block-sanding process in the sense that it flattens peaks to match their respective valleys. The differences are largely sequence and scale. Block sanding precedes paint whereas color sanding follows it. Block sanding flattens broad inconsistencies that make a panel look wavy; color sanding flattens the nearly microscopic inconsistencies that make a panel appear grainy.
We refer to polishing separately but it in fact serves the same abrasive function as color sanding in the sense that it replaces one type of surface irregularity with another. Remember how Killmer sanded the panel with successively finer abrasives last month? Well, polishing literally picks up where sanding falls short.
Sanding can remove a lot of material rapidly but only to a point. Sandpaper and pads don't readily accept very fine abrasives and at one point very fine abrasives remove material painfully slowly. Polishing compounds, on the other hand, rely on a transfer vehicle like a cloth or polishing pad. Attach that pad to a high-speed rotary polisher, however, and even the finest abrasives will remove material faster than the blink of an eye, something that underscores careful technique.
The polishing process can't really correct minor errors made during the spraying stage but its ability to eliminate superficial flaws paint suffers from use is really what makes it shine, so to speak. "It doesn't matter how nice the paint came out if there are a bunch of tiny scratches or swirl marks in it," Killmer observes. "Most people don't see that until you point it out to them, but once you see it, that's all you can see."
One distinction bears mentioning at this point. Until now we've referred to polishing as the final stage in a sanding process but it isn't necessary to color sand a finish prior to polishing it. In fact, some applications don't lend themselves to color sanding. Previously color-sanded finishes may not benefit or even stand up to additional sanding. As mentioned last month, color sanding removes the thin coating that protects the elements in single-stage metallic finishes. Finally, some applications just don't warrant color sanding. Even if slightly flawed, a thick, hardwearing paint surface may suit a driver better than a thinner, perfect one. But just because a surface might have minor flaws doesn't mean it can't look dynamite. It doesn't correct flaws to the same extent but simply polishing a surface improves its appearance without greatly compromising it.
Killmer showed us two methods, one rotary and the other orbital. Like color sanding, the rotary method consists of three progressive stages. Almost all color-sanding processes require rotary polishing to develop a full shine, but as stated earlier not all surfaces require color sanding to achieve respectable results with a rotary polish. It's more intensive but it also yields potentially best results.
The orbital method has only one stage. It works perfectly well on a surface that's never been polished, but because it's a very fine stage it cannot remove heavy color-sanding marks or deep paint flaws. Because it removes cobweb-like scratches, swirl marks, and oxidation at very little risk to the surface, the orbital process represents the ideal low-risk maintenance method for pretty much anyone, regardless of experience.
Beyond the shine they yield, the processes' real beauty is its versatility. Between these color sanding and polishing processes there's truly something for everybody, from rank amateurs to seasoned pros.