The hairline grain is brushed into the stainless steel surface first, then the gold coating is applied through PVD — a vacuum deposition process that builds an ultra-thin film, typically under a micron thick. Because the coating is this thin, it follows the existing brush lines rather than filling them in the way paint or thicker electroplating would. That's what keeps the grain visible under the color and gives gold hairline its brushed-brass character, rather than the flat, uniform sheen of a painted or heavily plated surface.