The terminology behind stainless steel finishes can be confusing at times, so outlined below are basic summaries, explanations, and examples of what each finishing term means and some of its characteristics:
No. 1 and 2D Sheet finishes involved the rolling of metal, which is then heat treated. Both finishes result in a dull metal with a raw, non-uniform appearance that is often quite difficult to polish. These finishes are most commonly found in industrial applications in which high heat is a factor - such as heaters, furnaces, and kilns.
No. 2 Strip and 2B Sheet Finishes involve stainless steel that is cold-rolled, which produces a hazy, semi-reflective finish. The semi-reflective finish lends itself to easier polishing. It's often found in applications such as serveware, wheel covers, and sheet metal.
The No. 3 Finish is found on stainless steel applications that receive a final polish with 80-120 grit abrasives. This particular finish can be most commonly found on kitchen tools and other food processing equipment.
The No 4. Finish is essentially a further-polished No. 2 or No. 3 finish. This finish is typically achieved with abrasive materials between 120 and 320 grit. The color of the final No. 4 Finish depends on the abrasive material used, as Aluminum-Oxide will result in a yellower finish while Silicon-Carbide will yield a cooler blue finish. It can be found most commonly on appliances and kitchen equipment, elevator doors, and in dairy applications.
The No. 6 Finish starts with a No. 4, which is then brushed with an oiled abrasive. It is less reflective than No. 4 and has a dull, satin-like finish. It's rarely used in contemporary applications and is best exemplified by the gargoyles on the Chrysler Building.
Stainless steel with a No. 7 finish is highly-reflective finish usually achieved by buffing or sanding with 320-400 grit abrasives. The finish resembles a dull mirror, and is often used on ornamental trim.
The No. 8 Finish is very close to a mirror finish, but still has visible grit lines. It's usually achieved by sanding a No. 7 Finish with progressively finer abrasive grits before transitioning to machine buffing.