ForMatter/Finishes/polish/Mirror polish
finish_polish_mirror

Mirror polish

polish · mirror · #8 polish, buffed mirror, high polish, Ra ≤ 0.025 µm

The shiniest a metal gets without plating. Worked through finer and finer abrasives until the surface scatters no light — you see your face in it. The bezel of a stainless watch, the inside of a polished silver bowl, the show side of a chromed motorcycle tank.

Mechanical surface reduction across a sequence of abrasives — typically 320 → 600 → 800 → 1200 grit silicon carbide, then loose abrasive on cloth or felt buffs (tripoli, then rouge or diamond paste 6 → 3 → 1 → 0.25 µm). Achieved Ra ≤ 0.025 µm (≤ 1 µin). Vulnerable to fingerprints and micro-scratching; usually clear-coated or used on stainless / precious metals where light marring polishes out.

character — specular, cool, slick, shows every fingerprint, optical-grade reflective.

Finish properties

  • levelmirror
  • subcategorymechanical reduction
  • Ra (µm)0.025
  • Ra (µin)1
  • applies tometal
Simon Winchester (living — quote)

But its standards were disastrously imperfect, inaccurate, and wrong.

Winchester, *The Perfectionists: How Precision Engineers Created the Modern World* (HarperCollins, 2018), Chapter 7, 'Through a Glass, Distinctly'. On the Hubble Space Telescope's primary mirror — polished to the most perfect figure ever produced on Earth, against a measuring null corrector that was itself out of true by 1.3 mm. The mirror was 'precisely imprecise.'

Second life

reversibilityhigh — re-polish at any time; the surface is a state, not a coating.
blocks substrate recyclingno
renewabilityyes — re-polish removes patina, scratches, oxide; the same buffing wheel that made the surface refreshes it.

Editorial pass 2026-04-28.

Citations

  • url · https://en.wikipedia.org/wiki/Polishing_(metalworking)
  • standard · ASME B46.1 — Surface Texture (Surface Roughness, Waviness, and Lay)
  • book · Untracht, *Jewelry Concepts and Technology* (Doubleday, 1982), polishing chapter — abrasive sequence and buff selection.
  • book · Winchester, *The Perfectionists: How Precision Engineers Created the Modern World* (HarperCollins, 2018), Chapter 7 — the Hubble primary-mirror grinding-and-polishing failure as the canonical lesson that polish-perfection is meaningless without a trustworthy reference.