Surface gloss is an important quality parameter in paints, plastics, metals, ceramics, automotive products, packaging and coatings. Two surfaces may have almost identical colors but appear noticeably different if their gloss levels are different. Visual gloss assessment can vary depending on lighting, viewing angle and the observer. A gloss meter provides a more objective method by measuring surface gloss numerically using a defined measurement geometry. Gloss meters offered by manufacturers such as 3NH can be used for quality control across a wide range of materials and industries.
What Is a Gloss Meter?
A gloss meter directs light onto a surface at a specified angle and measures the light reflected in a defined direction.
Results are typically reported in:
GU – Gloss Units
Higher GU values generally indicate a glossier surface, while lower values indicate a more matte appearance. However, the measurement angle and applicable test method must also be considered.
How Is Surface Gloss Created?
When light reaches a surface, some is absorbed, some is scattered and some is reflected.
Smooth surfaces tend to produce stronger directional reflection and therefore appear glossier.
Rough or matte surfaces scatter more light in different directions.
Gloss can therefore be influenced by:
- surface roughness,
- coating structure,
- paint quality,
- surface texture,
- manufacturing process.
What Do 20°, 60° and 85° Mean?
The most common gloss measurement geometries are 20°, 60° and 85°.
60° – General-Purpose Measurement
The 60° geometry is commonly used as the general-purpose measurement angle for many surfaces.
20° – High-Gloss Surfaces
The 20° geometry provides better differentiation between highly glossy surfaces.
Typical examples include polished coatings and high-gloss automotive finishes.
85° – Low-Gloss and Matte Surfaces
The 85° geometry is useful for distinguishing between surfaces with relatively low gloss.
It is commonly considered for matte paints, plastics and coatings.
| Angle | General Application | Surface Type |
|---|---|---|
| 20° | High-gloss differentiation | Glossy |
| 60° | General gloss measurement | Medium/general |
| 85° | Low-gloss differentiation | Matte |
The required geometry should ultimately be selected according to the relevant test method or product specification.
What Is a Gloss Unit (GU)?
Gloss Unit (GU) is the measurement value reported by a gloss meter.
A GU value should not be interpreted directly as the percentage of reflected light. The measurement is based on a defined reference and geometry.
Therefore:
50 GU does not simply mean 50% reflection.
When comparing products, the same measurement angle and conditions should be used.
How Is Gloss Measured?
1. Check and Calibrate the Instrument
Before measurement, verify or calibrate the gloss meter using the appropriate calibration standard according to the manufacturer's instructions.
2. Prepare the Surface
The sample should be clean, dry and representative of the product.
Dust, fingerprints, oil and other contamination can influence measurements.
3. Position the Instrument
Place the measurement aperture correctly against the surface.
Curved or very small samples may require additional consideration depending on instrument geometry.
4. Take the Measurement
The instrument directs light onto the surface, measures the reflected light and displays the result in GU.
5. Measure Multiple Areas
A single measurement may not represent a non-uniform surface.
Multiple measurements at different locations can provide a more representative average and indicate surface variation.
Single-Angle vs. Three-Angle Gloss Meters
A single-angle gloss meter may measure only one geometry, such as 60°.
A three-angle gloss meter typically provides:
20° + 60° + 85°
measurements in one instrument.
Three-angle instruments can provide greater flexibility when a laboratory tests products ranging from highly glossy to very matte surfaces.
Where Are Gloss Meters Used?
Gloss measurement is commonly used in:
- paints and coatings
- plastics
- automotive
- metals
- ceramics
- furniture and wood
- paper
- printing
- packaging
- electronic product surfaces
It is particularly useful for monitoring consistency between production batches.
Is Gloss Measurement the Same as Color Measurement?
No.
A color measurement instrument evaluates parameters such as L*a*b* and ΔE.
A gloss meter evaluates the reflective appearance of the surface.
Two products may have very similar L*a*b* values but look different because their gloss levels differ.
For this reason, some quality-control processes evaluate both color and gloss.
What Should You Consider When Choosing a Gloss Meter?
Important selection criteria include:
- 20°, 60° and 85° measurement geometries
- measurement range
- repeatability
- measurement aperture
- sample surface characteristics
- calibration method
- data storage and software functions
- compatibility with applicable ASTM, ISO or other test methods
When selecting a 3NH gloss meter, the specifications should therefore be matched to the surface type and intended testing method.
Tips for Reliable Gloss Measurement
For more repeatable results:
- Calibrate the instrument correctly.
- Keep the measurement surface clean.
- Use the same measurement angle for comparisons.
- Measure samples under consistent conditions.
- Take multiple readings on non-uniform surfaces.
- Protect calibration standards from scratches and contamination.
- Follow the geometry required by the applicable test method.
Conclusion
A gloss meter provides an objective and numerical method for evaluating surface gloss.
In general:
20° → High-gloss surfaces
60° → General-purpose gloss measurement
85° → Matte and low-gloss surfaces
Selecting the correct measurement geometry, maintaining proper calibration and measuring samples consistently helps laboratories and manufacturers obtain more reliable, comparable and repeatable gloss measurements.
