Bore polishing is different from glazing in that it is not a chemical coating but the smoothing down of a bore area. Polishing is caused by carbon on a piston (usually above the top ring) being constantly rubbed up and down the bore physically polishing an area. Again blow-by will occur and possible ring scuffing. The engine has usually done a considerable amount of miles at this point and bore polishing is noticed at strip down. This has to be removed by re-honing before new rings can be fitted.