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Gloss (material appearance)

 
Gloss (material Appearance)

 
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Gloss (material appearance)
 
 
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Gloss is an optical property, which is based on the interaction of light with physical characteristics of a surface. It is actually the ability of a surface to reflect light into the specular direction. The factors that affects gloss are the refractive index of the material, the angle of incident light and the surface topography
Topography

Topography is the study of Earth's surface shape and features or those ofplanets, Natural satellite, and asteroids. It is also the description of such surface shapes and features ....
.

Gloss can be said as a view of material appearance
Visual appearance

The visual appearance of objects is given by the way in which they reflect and transmit light. The color of objects is determined by the parts of the spectrum of light that are reflected or transmitted without being absorbed....
. Materials with smooth surfaces appear glossy, while very rough surfaces reflect no specular light and therefore appear matt (British English
British English

British English or UK English is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere....
) or matte (American English
American English

PhonologyIn many ways, compared to English language in England, North American English is conservative in its phonology. Some distinctive accents can be found on the East Coast of the United States , partly because these areas were in contact with England, and imitated prestigious varieties of English English at a time when those varieties we...
).






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Gloss is an optical property, which is based on the interaction of light with physical characteristics of a surface. It is actually the ability of a surface to reflect light into the specular direction. The factors that affects gloss are the refractive index of the material, the angle of incident light and the surface topography
Topography

Topography is the study of Earth's surface shape and features or those ofplanets, Natural satellite, and asteroids. It is also the description of such surface shapes and features ....
.

Gloss can be said as a view of material appearance
Visual appearance

The visual appearance of objects is given by the way in which they reflect and transmit light. The color of objects is determined by the parts of the spectrum of light that are reflected or transmitted without being absorbed....
. Materials with smooth surfaces appear glossy, while very rough surfaces reflect no specular light and therefore appear matt (British English
British English

British English or UK English is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere....
) or matte (American English
American English

PhonologyIn many ways, compared to English language in England, North American English is conservative in its phonology. Some distinctive accents can be found on the East Coast of the United States , partly because these areas were in contact with England, and imitated prestigious varieties of English English at a time when those varieties we...
). Gloss is also expressed as lustre
Lustre (mineralogy)

Lustre is a description of the way light interacts with the surface of a crystal, rock , or mineral. For example, a diamond is said to have an adamantine lustre and pyrite is said to have a metallic lustre....
 in mineralogy
Mineralogy

Mineralogy is an Earth Science focused around the chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization....
, or sheen in certain fields of application.

Qualitative and quantitative view


Surface gloss is considered to be the amount of incident light that is reflected at the specular reflectance
Reflectivity

In photometry and heat transfer, reflectivity is the fraction of incident radiation Reflection by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength....
 angle of the mean of that surface. So, specular gloss is proportional to the reflectance of the surface.

The Fresnel formula gives the specular reflectance, , for an unpolarized light of intensity , at angle of incidence , giving the intensity of specularly reflected beam of intensity , while the refractive index of the surface specimen is .

The Fresnel equation is given as follows :

Surface roughness


Nanorough
Surface roughness in micrometer range influences the specular reflectance levels. The diagram on the right depicts the reflection at an angle on a rough surface with a characteristic roughness height . The path difference between rays reflected from the top and bottom of the surface bumps is:

When the wavelength of the light is , the phase difference will be:

If is small, the two beams (see Figure 1) are nearly in phase and therefore the specimen surface can be considered smooth. But when , then beams are not in phase and through interference, cancellation of each other will occur. Low intensity of specularly reflected light means the surface is rough and it scatters the light in other directions. If an arbitrary criterion for smooth surface is , then substitution into the equation above will produce:

This smooth surface condition is known as the Rayleigh criterion.

Gloss measurement


Specular reflection is measured with a specular glossmeter
Glossmeter

A glossmeter measures specular reflection. The light intensity is registered over a small range of the reflection angle. The intensity is dependent on the material and the angle of illumination....
. Unpolarised white light is concentrated by a condenser
Condenser

Condenser may refer to:*Condenser , a device or unit used to Condensation vapor into liquid. More specific articles on some types include:*Condenser microphone, a device that converts sound waves into an electrical signal....
 lens onto a field aperture
Aperture

In optics, an aperture is a hole or an opening through which light is admitted. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of ray that come to a focus in the ....
, which is located in the focal plane of the source lens. The reflected beam at the surface is later collected by the receptor lens. The intensity of the beam is then measured through a photodetector.

The common angles of incidence for gloss measurement are 20°, 60° and 85°. In some cases 45° and 75° geometry is used. Low gloss surfaces are recommended to be measured with 85° settings.

The typical standards
Standards organization

A standards organization, standards body, standards development organization or SDO is any entity whose primary activities are developing, coordinating, promulgating, revising, amending, reissuing, interpreting, or otherwise maintaining standards that address the interests of a wide base of users outside the standards develo...
 for gloss measurements are ASTM
ASTM International

ASTM International , originally known as the American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services....
 D 2457, DIN EN ISO 2813 and DIN
Din

DIN or Din or din can have several meanings:-* A din is a loud noise.* Deen , an Arabic language term meaning "religion" or "way of life"....
 67530.

See also

  • List of optical topics
    List of optical topics

    Probably some Wikipedia articles on topics in optics are not yet listed on this page. If you cannot find the topic you are interested in on this page, the article may nonetheless exist; you can try to find it using the "Search" box, or look in :Category:Optics and its subcategories....
  • Visual appearance
    Visual appearance

    The visual appearance of objects is given by the way in which they reflect and transmit light. The color of objects is determined by the parts of the spectrum of light that are reflected or transmitted without being absorbed....
  • Glossmeter
    Glossmeter

    A glossmeter measures specular reflection. The light intensity is registered over a small range of the reflection angle. The intensity is dependent on the material and the angle of illumination....