Faqs
Summary FAQ's
How is gloss measured?
Why measure gloss?
What difference in gloss units is visable to the human eye?
How can I measure the gloss of curved surfaces?
How is gloss measured?
Gloss is measured by shining a known amount of light at a surface and quantifying the reflectance. The angle of the light and the method by which the reflectance is measured are determined by surface and also aspect of the surface appearance to be measured.
UpWhy measure gloss?
Gloss is an aspect of the visual perception of objects that is as important as colour when considering the psychological impact of products on a consumer.
It has been defined as ‘The attribute of surfaces that causes them to have shiny or lustrous, metallic appearance.’
The gloss of a surface can be greatly influenced by a number of factors, for example the smoothness achieved during polishing, the amount and type of coating applied or the quality of the substrate.
Manufacturers design their products to have maximum appeal- highly reflective car body panels, gloss magazine covers or satin black designer furniture.
It is important therefore that gloss levels are achieved consistently on every product or across different batches of products.
Gloss can also be a measure of quality of a surface, for instance a drop in the gloss of a coated surface may indicate problems with its cure- leading to other failures such as poor adhesion or lack of protection for the coated surface.
It is for these reasons that many manufacturing industries monitor the gloss of their products, from cars, printing and furniture to food, pharmaceuticals and consumer electronics.
UpWhat difference in gloss units is visable to the human eye?
If two different coatings are measured, what number of gloss units would be detectable by the human eye, how many units would be perceived as significantly different?
When measuring at 60 Degrees these detectable differences depend on the gloss level of the sample, for instance 3.0 GU difference measured on a very matt surface (perhaps 5GU), would be seen by the human eye but on a higher gloss coating (perhaps 60 GU) the difference would be very difficult to notice.
The only way that you can determine tolerances for your products would be experimentally, perhaps preparing printed samples at different gloss levels that you can show to end users of your coatings or internal “experts”
The other option is to change to a 20/60/85 degree instrument, the 85 degree glossmeter is more sensitive to differences in gloss below 10 GU @ 60º and the 20 Degrees has higher resolution on high gloss coatings (above 70 GU @ 60º). The advantage of using the three angles is that there is more equality to the gloss differences, in our experience a gloss difference of 5 GU, when measured with the correct geometry is just visible to a trained observer.
UpHow can I measure the gloss of curved surfaces?
All standard gloss meters are designed for flat surfaces, if they are used on a curved surface, the measurement beam is reflected away from the instrument detector resulting incorrect readings. The more curved the surface the greater the error.
The solution to this problem is to using a very small area. The light is slightly scattered by the curved surface, however as long as the reflected beam remains sufficiently narrow to remain within the instrument detector the reading will be correct. The Novo-Curve gloss meter has been designed for this purpose and is specified for measuring cylinders and spheres with very low diameters. The Novo-Curve was developed in conjunction with the National Physics Laboratory (NPL).
ISO 2813 and ASTM D523 (the most commonly used standards) describe three measurement angles for the measurement of gloss across surfaces of all levels.
The standard gloss unit (GU) is used, this is traceable to standards held at BAM (Germany), NRC (Canada) or NPL (UK).
Universal Measurement Angle- 60º
All gloss levels can be measured using the standard measurement angle of 60º. This is used as the reference angle with the complimentary angles of 85º and 20º often used for low and high gloss levels respectively.
Low Gloss- 85º
For improved resolution of low gloss a grazing angle of 85º is used to measure the surface. This angle is recommended for surfaces which measure less than 10 GU when measured at 60º.
This angle also has a larger measurement spot which will average out differences in the gloss of textured or slightly uneven surfaces.
High Gloss- 20º
The acute measurement angle of 20º gives improved resolution for high gloss surfaces. Surfaces that measure 70 GU and above at the standard angle of 60º are often measured with this geometry.
The 20º angle is more sensitive to haze effects that affect the appearance of a surface.
What gloss standard should I be using to measure gloss?
Many industries have adopted the 20/60/85º geometries as specified in ISO2813/ ASTM D523, however consult the table below for more information on specific industries and their industrial standards.
General Gloss measurement
ASTM D523 1999 (USA)
Test method for specular gloss
The principal ASTM specular gloss standard. Very similar to ISO 2813
ASTM D3928 1998 (USA)
Test method for evaluation of gloss or sheen uniformity
ASTM D4039 1999 (USA)
Test method for reflection haze of high-gloss surfaces
ASTM D4449 1999 (USA)
Test method for visual evaluation of gloss differences between surfaces of similar appearance
ASTM D5767 1999 (USA)
Test methods for instrumental measurement of distinctness of image gloss of coating surfaces
ASTM E340 1997 (USA)
Test methods for measurement of gloss of high-gloss surfaces by goniophotometry
ASTM E340 1997 (USA)
Test methods for measurement of gloss of high-gloss surfaces by goniophotometry
MFT 30-064 (South Africa)
Local version of ASTM D523
JIS Z8741 1997 (JAPAN)
Method of measurement for Specular glossiness
IS0 2813 1994 (International)
Paints and varnishes - determination of specular gloss of non-metallic paint films at 20°, 60° and 85°
The principal ISO specular gloss standard. Very similar to ASTM D523.
The following are technically similar to ISO 2813:
BS 3900: Part D5 1995 (UK)
Methods of test for paints - optical tests on paint films - measurement of specular gloss of non-metallic paint films at 20°, 60° and 85°
DIN 67530 1982 (Germany)
Reflectometer as a means for assessing the specular gloss of smooth painted and plastic surfaces
NFT 30-064 1999 (France)
Paints - measurement of specular gloss
at 20, 60 and 85°.
AS 1580 MTD 602.2 1996 (Australia)
Paints and related materials, methods of test – introduction and list of methods.
JIS Z8741 1997 (Japan)
Specular glossiness – Method of measurement.
SS 18 41 84 1982 (Sweden)
Paints and varnishes - measurement of specular gloss of non-metallic paint films at 20, 60 & 85°
BS 2782: Pt 5, Method 520A 1992
Methods of testing plastics - optical and colour properties, weathering - determination of specular gloss
Similar to ISO 2813
ASTM D2457 1990
Test Method for Specular Gloss of Plastic Films and Solid Plastics
Specifies the primary standard as a perfect mirror with a defined gloss value of 1000. 20°, 60° and 45°; the 45° method is as ASTM C346 for ceramics.
BS6161: Part 12 1987
Methods of test for anodic oxidation coatings on aluminium and its alloys - measurement of specular reflectance and specular gloss at angles of 20°, 45°, 60° or 85°
Ref. Std BS 3900: Part D5 (1980); technically equivalent to ISO 7668; replaces BS 1615:1972. At 45°, dimensions of source image and receptor aperture are as for 60°. Squares with sides equal to the shorter sides of the rectangles are also recommended. Alternatively, total reflection in a 45° prism is used as a reference; source image and receptor aperture are then circular, both with angular diameter 3.44° ± 0.23° (
IS0 7668 1986
Anodized aluminium and aluminium alloys - measurement of specular reflectance and specular gloss at angles of 20°, 45°, 60° or 85°.
IS0 5190
Anodizing of aluminium and its alloys - evaluation of uniformity of appearance of architectural anodic finishes - determination of diffuse reflectance and specular gloss
ECCA T2 (European Coil Coating Association)
Specular gloss at 60°.
DIN 54502 1992
Testing of paper and board; reflectometer as means for gloss Assessment of paper and board
ASTM D1223 1998
Test method for specular gloss of paper and paperboard at 75°.
Has unusual converging beam geometry. Specifies the primary standard as black glass of refractive index 1.540, not 1.567, at the sodium D-line having a defined gloss value of 100.
ASTM D1834 1995
Test method for 20° specular gloss of waxed paper
Another unusual converging beam geometry, different to the previous one.
TAPPI T480 OM-90 1990 (USA)
Specular gloss of paper and paperboard at 75°
Same text as ASTM D 1223
TAPPI 653 1990
Specular gloss of waxed paper and paperboard at 20°
Probably the same text as ASTM D 1834
JIS - Z8142 1993 (Japan)
Testing method for 75° specular gloss
BS 3962: Part 1 1980
Methods of test for finishes for wooden furniture - assessment of low angle glare by measurement of specular gloss at 85°
Similar to ISO 2813: 1978
ASTM D1455 1987
Test method for 60° specular gloss of emulsion floor polish
Ref. std ASTM D 523
ASTM C346 1987
Test method for 45° specular gloss of ceramic materials
Ref. std ASTM D 523
ASTM C584 1981
Test method for 60° specular gloss of glazed ceramic whitewares and related products
Ref. std ASTM D 523
BS 3424: Method 31: Part 28 1993
Testing coated fabrics - determination of specular glossUpBack
