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 surf ...

(still limited by the

index of refraction In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

of the material according to the

Fresnel equations The Fresnel equations (or Fresnel coefficients) describe the reflection and transmission of light (or electromagnetic radiation in general) when incident on an interface between different optical media. They were deduced by Augustin-Jean Fresne ...

). In some materials (such as metals, glasses, black or transparent stones), polishing is also able to reduce

diffuse reflection Diffuse reflection is the reflection (physics), reflection of light or other radiation, waves or particles from a surface such that a ray (optics), ray incident on the surface is scattering, scattered at many angles rather than at just one angle ...

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

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

s starts with a coarse

grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refer ...

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 concentration In solid mechanics, a stress concentration (also called a stress raiser or a stress riser) is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregularitie ...

s 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 Mass finishing is a group of manufacturing processes that allow large quantities of parts to be simultaneously finished. The goal of this type of finishing is to burnish, deburr, clean, radius, de-flash, descale, remove rust, polish, brighten, surfa ...

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 Vibratory finishing is a type of mass finishing manufacturing process used to deburr, radius, descale, burnish, clean, and brighten a large number of relatively small workpieces.Degarmo, p. 783. In this batch-type operation, specially shaped pell ...

Sodablasting Soda blasting is a mild form of abrasive blasting in which sodium bicarbonate particles are blasted against a surface using compressed air. It has a much milder abrasive effect than sandblasting. An early use was in the conservation-restoration ...

Woodworking

French polishing French polishing is a wood finishing technique that results in a very high gloss surface, with a deep colour and chatoyancy. French polishing consists of applying many thin coats of shellac dissolved in denatured alcohol using a rubbing pad lubri ...

Wood finishing Wood finishing refers to the process of refining or protecting a wooden surface, especially in the production of furniture where typically it represents between 5 and 30% of manufacturing costs. Finishing is the final step of the manufacturing ...

Other

Chemical-mechanical polishing Chemical mechanical polishing (CMP) or planarization is a process of smoothing surfaces with the combination of chemical and mechanical forces. It can be thought of as a hybrid of chemical etching and free abrasive polishing. Description The proc ...

, which is used in semiconductor fabrication *

Fabrication and testing of optical components Optical manufacturing and testing spans an enormous range of manufacturing procedures and optical test configurations. The manufacture of a conventional spherical lens typically begins with the generation of the optic's rough shape by grinding a ...

Flame polishing Fire polishing, also known as flame polishing, is a method of polishing a material, usually glass or thermoplastics, by exposing it to a flame or heat. When the surface of the material briefly melts, surface tension smooths the surface. Operator sk ...

, a type of polishing used on glass and thermoplastics * Ultra-fine, abrasive paste polishing, polishing for soft or fragile work surfaces *

Vapor polishing Vapor polishing is a method of polishing plastics to reduce the surface roughness or improve clarity. Typically, a component is exposed to a chemical vapor causing the surface to flow thereby improving the surface finish. This method of 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