Summary for mirror finish Discussion
Cottonball and mirror finish is discussed as a subjective appearance term rather than a fixed technical standard. Perry Snook asks how such a finish is achieved and whether an industry specification exists. The reply says the question partly answers itself: standards may be numerical or visual, but what looks like a mirror to one person may only seem bright to another. Even a low numerical RMS value does not necessarily guarantee a reflective mirror finish. The answer frames "mirror" as more like an adjective than a precise noun, implying that any specification would need to define the desired appearance or measurement criteria very carefully. No specific process steps or formal industry standard are given in the thread excerpt.
Q. How is a cottonball / mirror finish achieved?
Is there an existing industry standard/specification?
Perry Snook
– Canada
2006
? Question about your question. You kind of answered the question yourself. Standards can be numerical evaluations or visual to the person. What is mirror to one person may only be bright to another. Even a low numerical RMS may not be a reflective mirror finish. Therefore, it is something like describing an adjective rather than a noun type word, if that makes any sense either.
AF Kenton
retired business owner – Hatboro, Pennsylvania
2006
A. I agree with Mr. Kenton. The closest you’ll get to a mirror standard is a sample plate produced by any of the specialists on surface finishes and a pair of trained 20/20 vision eyes. For inspection purposes, that’ll be about all you need. If your interest is in producing that specific finish on a large number of metal parts, approach a mass finisher specialist. If you want to mirror polish a prototype or small run of large, heavy and complicated geometry parts, maybe we can help.
Guillermo Marrufo
Monterrey, NL, Mexico
2006
Q. What Ra will provide a cotton-ball finish on a 316L SS surface?
[What finish will not pull fibers out of a cotton ball slid over the surface? Ra16 µ-inch or smother?]
Ken Schroeder
– Grand Rapids Minnesota
September 1, 2020