Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant
specular reflection
Specular reflection, or regular reflection, is the mirror-like reflection of waves, such as light, from a surface.
The law of reflection states that a reflected ray of light emerges from the reflecting surface at the same angle to the su ...
(still limited by the
index of refraction of the material according to the
Fresnel equations). In some materials (such as metals, glasses, black or transparent stones), polishing is also able to reduce
diffuse reflection
Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection. An ''ideal'' ...
to minimal values.
When an unpolished surface is magnified thousands of times, it usually looks like a succession of mountains and valleys. By repeated abrasion, those "mountains" are worn down until they are flat or just small "hills." The process of polishing with
abrasives starts with a coarse
grain size and gradually proceeds to the finer ones to efficiently flatten the surface imperfections and to obtain optimal results.
Mechanical properties
The strength of polished products can be higher than their unpolished counterparts owing to the removal of
stress concentrations present in the rough surface during the polishing process. These concentrations take the form of corners and other defects, which magnify the local stress beyond the inherent strength of the material.
Types
Metalworking
Other polishing processes include:
*
Burnishing
*
Mass finishing
**
Tumble finishing
Tumble finishing, also known as tumbling or rumbling, is a technique for smoothing and polishing a rough surface on relatively small parts. In the field of metalworking, a similar process called barreling, or barrel finishing,Degarmo, p. 781. wo ...
**
Vibratory finishing
*
Sodablasting
Woodworking
*
French polishing
*
Wood finishing
Other
*
Chemical-mechanical polishing, which is used in semiconductor fabrication
*
Fabrication and testing of optical components
*
Flame polishing, a type of polishing used on glass and thermoplastics
* Ultra-fine, abrasive paste polishing, polishing for soft or fragile work surfaces
*
Vapor polishing, a method of polishing plastics to optical clarity
References
External links
{{wiktionary
Decorative arts
Grinding and lapping
Industrial processes
Wood finishing techniques
Surface finishing