Sheen is a measure of the reflected light ( glossiness) from a

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

finish. ''Glossy'' and ''flat'' (or ''matte'') are typical extreme levels of glossiness of a finish. Glossy paints are shiny and reflect most light in the

specular 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 surfac ...

(mirror-like) direction, while on flat paints most of the light diffuses in a range of angles. The gloss level of paint can also affect its apparent colour. Between those extremes, there are a number of intermediate gloss levels. Their common names, from the most dull to the most shiny, include ''matte'', ''eggshell'', ''satin'', ''silk'', ''semi-gloss'' and ''high gloss''. These terms are not standardized, and not all manufacturers use all these terms.

Terminology

Firwood, a UK paint manufacturer measures gloss as percentages of light reflected from an emitted source back into an apparatus from specified angles, ranging between 60° and 20° depending on the reflectivity. With very low gloss levels (such as matte finishes), a 60° angle is too great to measure light reflectance accurately, so a lower angle of 20° is usually used. The returned light into the apparatus allows the gloss to be classified as follows: * Full gloss: 70–90% * Semi-gloss: 41–69% * Satin: 26–40% * Sheen: 15–25% * Eggshell: 10–15% * Matte: <10%

Technology

The sheen or gloss level of a paint is principally determined by the ratio of resinous, adhesive binder, which solidifies after drying, and solid, powdery

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

. The more binder the coating contains, the more regular reflection will be made from its smooth surface; conversely, with less binder, grains of pigment become exposed to the surface, scattering the light and providing matte effect. To a lesser extent, gloss is also affected by other factors: refraction index of the pigment particles, viscosity and refraction index of the binder. An important indicator is ''pigment-volume concentration'' (PVC), defined as the ratio of pigment volume and total paint volume: :

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PVC affects both physical and optical properties of a paint. Matte paints have less binder, which makes them more susceptible to mechanical damages (however, they are less visible than on glossy surfaces). More binder provides a smoother and more solid surface. However, at a certain PVC, called ''critical PVC'' (CPVC), the paint is already saturated with binder and the surface becomes solid and glossy, without protruding particles; adding more binder (lowering PVC) will not affect the sheen. CPVC generally depends on the binder-pigment system used, and generally falls in the 35–65% range. As a gloss finish will reveal surface imperfections such as sanding marks, surfaces must generally be prepared more thoroughly for gloss finishes. Gloss-finish paints are generally more resistant to damage than flat paint, more resistant to staining, and easier to clean.Koleske, Paint and Coating Testing Manual, p. 615, Flat paint may become glossier through burnishing or staining with grease; glossy paint may lose its gloss and look scratched if abraded. Unlike gloss paint, flat paint can generally be touched up locally without repainting the entire surface. Gloss level can be characterized by the angular distribution of light scattered from a surface, measured with a

glossmeter A glossmeter (also gloss meter) is an instrument which is used to measure specular reflection gloss of a surface. Gloss is determined by projecting a beam of light at a fixed intensity and angle onto a surface and measuring the amount of reflect ...

, but there are various ways of measuring this, and different industries have different standards.

Applications

In traditional household interiors, walls are usually painted in flat or eggshell gloss, wooden trim (including doors and window sash) in high gloss, and ceilings almost invariably in flat. Similarly, exterior trim is usually painted with a gloss paint, while the body of the house is painted in a lower gloss. Gloss paint is commonplace in the automotive industry for car bodies.

References

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External links

PCI Magazine article: What is the Level of Confidence in Measuring Gloss?NPL: Good practice guide for the measurement of Gloss
Interior design Painting materials