Paint correction stages, decoded: what the machine is actually doing
Paint correction is controlled abrasion. A machine polisher works a pad and an abrasive compound across the clearcoat, levelling the surface down to the depth of the deepest defect being removed. A swirl mark is a valley in the clearcoat; the machine removes the surrounding peaks until the surface is uniform again and light reflects cleanly. This is why correction is finite: each pass spends clearcoat you cannot get back, and why the depth-gauge readings from the walkaround matter so much.
The stage terminology is loose across the market, so pin down what is included rather than trusting the label. A single-stage polish (often sold as an enhancement) uses one finishing polish to boost gloss and remove light swirls — the bulk of light visible defects — and suits most daily drivers. A two-stage correction adds a heavier cutting compound first to tackle deeper scratches and etching, then refines the haze that cutting leaves behind. Multi-stage work, sometimes involving wet sanding for deep defects, is show-car territory. One vendor's stage two is another's stage one plus marketing, so ask what percentage of defect removal they are targeting and how they will demonstrate it.