Of particular note are the gloss and sheen levels required for approval. The levels are important from performance and appearance aspects, and therefore are now shown above the specific category. New standards have been established to realign gloss levels in latexes to those retained in alkyds. MPI has moved away from traditional names for gloss levels as these names and levels differ from manufacturer to manufacturer. In order to provide some method of comparing some of the merits of one product to another, it became obvious that levels not names, were needed in MPI categories.
MPI Gloss and Sheen Standards are now as follows:
|Gloss at 60 degrees||Sheen at 85 degrees|
|Gloss Level 1||a traditional matte finish - flat||maximum 5 units||and||maximum 10 units|
|Gloss Level 2||a high side sheen flat - a 'velvet-like' finish||maximum 10 units||and||10-35 units|
|Gloss Level 3||a traditional 'eggshell-like' finish||10-25 units||and||10-35 units|
|Gloss Level 4||a 'satin-like'finish||20-35 units||and||minimum 35 units|
|Gloss Level 5||a traditional semi-gloss||35-70 units|
|Gloss Level 6||a traditional gloss||70-85 units|
|Gloss Level 7||a high gloss||more than 85 units|
What is Gloss and Sheen ?The term 'gloss" is used in many contexts. A gloss finish indicates that it is shiny or glass-like. The gloss of a finish suggests a level of gloss from flat to gloss or 'glossy'. The gloss of a surface is described as the reflection of light from the surface that is independent of color. This is also known as the "objective gloss".
To measure gloss reflectance, a single beam of light is deflected off the surface, at a prescribed angle, into a receptor. This receptor gauges the intensity of that light in gloss units. The testing equipment is standardized by the use of specially produced, polished, glass or ceramic tiles. The higher the number of units, the shinier the surface. ASTM method D 523 outlines the procedures for performing the test.
The ASTM method uses the 60° geometry both for comparing surfaces and to determine whether the 20° or 85° geometry is warranted. The 20° is used when the sample has a 60° gloss greater than 70, and the 85° is used if the 60° gloss is less than 30. Both the 20° and 85° geometry were added to method D 523 in 1953.
The most common angle used by the coatings industry to break up the basic divisions of gloss is 60° from the perpendicular (or 30° above the plane). It gives a good general evaluation of gloss except at the extremes of low and high gloss surfaces.
For the most part, sheen is used to describe the low angle gloss (85° from the perpendicular, or 5° above the plane) of a surface. Variances in the sheen of a surface are most noticeable in low gloss coatings. Measurements at this angle are generally thought to be a more accurate indicator of the transition between flat and eggshell.
Steep angles, such as 20°, are most often used for surfaces with a "high gloss", such as automotive and Original Equipment Manufacturer's (OEM) finishes.
The gloss level of a coating is influenced by surface roughness. In a paint or coating, the protrusion of pigment particles through the resin or binder layer causes the diffraction of the light, and a dullness is visible. Where the pigment is completely coated by the resin, the surface is smoother and the angular light is reflected unhindered, producing a glossy appearance, not unlike a polished glass surface.
As gloss is a property of reflected light, it can influence the visual color of a surface when viewed from various angles. This is commonly seen where coatings that have been tinted to the same color, but have different gloss levels, are applied side by side on the same substrate. Viewing from a position directly perpendicular from the surfaces, with the light directly behind, will show the closest color. Moving to an angle away from the perpendicular (or moving the light source), will show a color difference caused by the difference in gloss. When a coating surface has a 60° and 85° gloss that are the same (or very similar), the uniformity in appearance is apparent from all angles. This reduces visible shading effects from slightly non-uniform surfaces.
An example of this in day-to-day situations would be a long hallway. The optimum situation would be a wall coating where the gloss reflectance is the same (or very similar) at both 60° and 85°. With this a person walking along the hall would not notice a sheen difference even though the angle to the wail was ever changing as the person continued walking.
Where color and white reflection are measured, two light sources are used. These are angled at 45 degrees on opposite sides of a central receptor. The receptor is split up into individual detectors that are each responsive to a different primary color. This is referred to as 0/45 or 45/0/45° geometry. Most color testing equipment uses this geometry to avoid the influence of gloss while measuring the color.
Other TermsDistinctiveness Of Image (DOI)
- The DOI of a surface is described as the clarity of a reflected (mirror -like) image in the surface. This property is tested on very glossy, smooth surfaces such as automotive coatings.
- A term used to describe the shine, gloss, sheen or brilliance of a surface (e.g. low luster)
- A Flat finish
Gloss RangesIn the earlier days of commercial paint manufacture, the ranges for gloss were limited to flat, semi-gloss, and gloss. Since then, many manufacturers developed subdivisions of these, particularly between Flat and semi-gloss. As many of these subdivisions were made on a regional basis, there are now many deviations from a uniform categorization. For example, according to one manufacturer satin is between 6 and 12 units at 60°, whereas another lists it as from 15 to 25 units at the same 60°. Some have it below eggshell, and still others have it above eggshell measured at the same angle. Among various other gloss names created are platinum, pearl, melamine, velvet, eggshell, and satin. The names were chosen presumably to reflect the very literal, but very subjective, description of the surface.
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